The Holiday this year has been updated with ilevel 540 loot plus several new rewards, including new battle pets and "costumes".  WowHead has put together a guide:

Hallow's End (October 18 - November 1)

Event Changes

After a draught of holiday updates, Hallow's End has some new loot in 2014!

Hallow's End loot is now ilvl 540, to get players ready for Warlords of Draenor. Inside the  Loot-Filled Pumpkin, you can find:

• The Horseman's Ring
• Seal of Ghoulish Glee
• Band of the Petrified Pumpkin
• Wicked Witch's Signet
• The Horseman's Sinister Slicer
• The Horseman's Horrific Hood

View the rest of the thread for the full information ...

and the rest of the guide ...

Also tied to the event is the amazing costume  Exquisite Costume Set: "The Lich King", new wands such as  Hallowed Wand - Slime, new battle pets  Widget the Departed and  Cursed Birman, and several pug disguises ( "Mad Alchemist" Costume,  "Lil' Starlet" Costume,  "Yipp-Saron" Costume). We'll update this guide when the event goes live with more details on the new items, including source and location.

There are costs listed on Chinese Battle.net but they sound a bit high and may not be the same for US/EU realms.

In addition,  Little Wickerman is now classified as a toy to fit into your brand-new Toy Box!

Tricky Treats Loot

Since 2011, gone are the days of trick-or-treating hourly for a chance at an extremely rare mask or a rare vanity item. Instead, the event has been streamlined into a vendor and daily system, very similar to Noblegarden. One vanity pet,  Feline Familiar, makes its appearance here on a vendor, for example; meanwhile, old favorites, such as  Sinister Squashling are purchasable. There's also  Creepy Crate from a short questline and  Little Wickerman from vendors which is a fun campfire.

Tricky treats are obtained through dailies and the pumpkins spread throughout inns on the map. You will get two treats for every inn you visit as a one-time only reward, along with a potential for a mask, wand, or other fun holiday item. You then spend the tricky treats at vendors outside of your capital cities.

Vendors and quest-givers are located at special holiday hubs outside of Stormwind and Undercity.

• Horde: Chub , Darla , Farina .
• Alliance: Dorothy , Stymie , Spanky .

Vendor Items

Hallowed Wands

Item	Vendor	Cost
Hallowed Wands	Stymie or Darla	2 each

Consumables

Chewy Fel Taffy x5	Dorothy or Chub	2
Pyroblast Cinnamon Ball x5	Dorothy or Chub	2
Soothing Spearmint Candy x5	Dorothy or Chub	2
G.N.E.R.D.S. x5	Dorothy or Chub	2
Tooth Pick x10	Dorothy or Chub	2

Pets and Mounts

Magic Broom	Dorothy or Chub	150
Sinister Squashling	Dorothy or Chub	150
Feline Familiar	Dorothy or Chub	150
Cursed Birman	Dorothy or Chub	150
Widget the Departed	Dorothy or Chub	150

Misc

Hallowed Helm	Dorothy or Chub	150
Little Wickerman	Dorothy or Chub	150

Masks

Playable race masks (24 total)	Spanky or Farina	2 each
Non-playable race masks (8 total)	Spanky or Farina	5 each

Battle Pets

Hallow's End has five festive battle pets, four of which can be caged and sold on the AH:

•  Sinister Squashling teaches the elemental pet Sinister Squashling, with breed 10 P/B. Burn, Thorns, Plant, Poison Lash, Stun Seed, Leech Seed
•  Feline Familiar teaches the beast pet Feline Familiar with breed 10 P/B. Onyx Bite, Stoneskin, Devour, Pounce, Call Darkness, Prowl
•  Creepy Crate teaches the undead pet Creepy Crate with breed 6 H/H. Creepy Chomp, Death Grip, Devour, Agony, Curse of Doom, BONESTORM. This pet is not cageable, meaning you will have to do the Creepy Crate questline in order to obtain it.

In 2014, there are two more pets:

•  Cursed Birman teaches the undead pet Cursed Birman. Pounce, Call Darkness, Devour, Spirit Claws, Spirit Spikes, Prowl
•  Widget the Departed teaches the undead pet Widget the Departed. Pounce, Devour, Call Darkness, Spirit Claws, Spectral Strike, Prowl

There are also three  Perky Pug disguises:  "Mad Alchemist" Costume,  "Lil' Starlet" Costume,  "Yipp-Saron" Costume.

Candy

Those candies you get from trick-or-treating have changed several times over WoW's history. They used to be buffs, offering amounts of stacking stats such as spell power with every consumption. However, that's changed and they now provide only visual effects.

•  Pyroblast Cinnamon Ball: red halo
•  Chewy Fel Taffy: swirling skulls like Unholy Weapon
•  Soothing Spearmint Candy: icy blue snowflakes
•  G.N.E.R.D.S.: yellow lightbulb

You can also purchase  Hallow's End Pumpkin Treat from Katrina Shimmerstar and Rachelle Gothena. This candy has 4 possible effects:

• Hallow's End Candy: Large and orange, 5% chance to increase time between attacks by 25% and reduce movement speed by 30%
• Hallow's End Candy: Skeleton transformation and underwater breathing
• Hallow's End Candy: Pirate disguise and 50% swim speed increase
• Hallow's End Candy: Spectral tint and levitate

Toys

 Little Wickerman is now classified as a Toy, which means you can put it in your Toy Box collection. This makes the toy account-wide and more importantly, frees up a bag slot!

Wands

Unlike many other Hallow's End consumables, wands do not require the event to be active in order to use them, so you can have fun disguises all year long.

•  Hallowed Wand - Pirate
•  Hallowed Wand - Ninja
•  Hallowed Wand - Leper Gnome
•  Hallowed Wand - Ghost
•  Hallowed Wand - Bat
•  Hallowed Wand - Skeleton
•  Hallowed Wand - Random
•  Hallowed Wand - Wisp

Five more have been added in 2014:

•  Hallowed Wand - Spider
•  Hallowed Wand - Geist
•  Hallowed Wand - Abomination
•  Hallowed Wand - Slime
•  Hallowed Wand - Ghoul

Masks

2011 added many new masks. First and foremost for the two playable races added in Cataclysm:

Sadly there seem to be no pandaren masks. This brings the amount of masks for playable races up to 24.

In addition to the playable race masks, there are also four sets based on non-playable races; these masks have buffs. Because they function as buffs, they cost more to purchase and are probably meant items for the player who has nearly everything as a currency sink.

New Buffs

Two powerful buffs are tied to the Wickerman Festival. Every four hours there is a city-wide announcement and then 10 minutes later, Sylvanas or Genn buffs nearby players.

Decree of the Dark Lady is granted to nearby players upon observing an RP event in which Sylvanas watches the burning of the Wickerman and declares it to be a sign of the strength of the Forsaken. It lasts an hour and persists through death. Level 1-79 players receive a non-mastery version, Decree of the Dark Lady.

Greymane's Resolve works in the same way for Alliance players--Genn Greymane watches the burning of the Wickerman and celebrates the resilience of the Worgen. It lasts an hour and persists through death. Level 1-79 players receive a non-mastery version, Greymane's Resolve.

You can also obtain Unburdened/ Grim Visage and is easily gotten--just use the ashes on the ignited Wickerman bonfire outside Stormwind or Undercity. The experience bonus works on mob kills only, and the reputation bonus works on everything. The reputation bonus also stacks with other bonuses like Diplomacy and Mr. Popularity.

If the ashes are not available, wait for someone to finish A Time to Build Up or an NPC to rekindle it.

Treats and Goodies!

Acquiring Items

There are three main ways players can acquire quirky seasonal items during the Hallow's End festival:
Candy Buckets,  Crudely Wrapped Gift, and the Headless Horseman.

Candy Buckets (in the shape of pumpkins) are nearby the innkeepers of friendly inns. Instead of talking to an innkeeper each hour for a Treat Bag or a Trick disguise as in the past, looting each pumpkin will reward players with a  Handful of Treats (and sometimes a temporary character disguise, like the Trick debuff--do keep in mind this silence/pacifies you). This contains 1-3  Tricky Treat, some candy, and other vanity items. If you don't get lucky with finding rare items in your candy bags, don't worry--the  Tricky Treat can be used to purchase them instead. This system takes the RNG component out of the holiday that many had complained about.

(As in past years, there's also an Apple Bob nearby, which gives players  Bobbing Apple.)

A  Crudely Wrapped Gift can be obtained after protecting a low level Alliance (Goldshire, Kharanos, or Azure Watch) or Horde (Razor Hill, Falconwing Square, or Brill) village from the Shade of the Horseman (see Quests section below). The matrons located in these villages will ask for your aid in putting out fires in local buildings. When the Shade of the Horseman has been defeated, a large Jack-o-Lantern will appear on the ground that gives the quest Smash the Pumpkin (Alliance) which can be turned in at the nearby Matron. The Matron will reward you with a sum of gold and a  Crudely Wrapped Gift, which can contain candy, masks, or even riding brooms!

The Headless Horseman is a level 90 boss that players can queue up for using the Dungeon Finder tool. The boss will then spawn in the Graveyard of Scarlet Monastery. This encounter can be completed easily by a decently-geared 5-man of level 90 players. For more information check out the section below!

 Tricky Treat Currency

Since 2014 offers new items, we wanted to break down how many  Tricky Treat you'll need to get everything you want. Note: this section may be updated when we can confirm sources and costs for all new 2014 items.

• New to 2014 loot: if you want to get the two new battle pets and 5 new wands, it will cost you 310  Tricky Treat.
• All the battle pets: four battle pets will cost you 600  Tricky Treat.
• Items needed for Hallowed Be Thy Name achievements: ~323. 14 for The Masquerade, 300 for Sinister Calling, 2 for That Sparkling Smile, ~5 for Out With It, ~2 for G.N.E.R.D. Rage.
• Items needed for all the Hallow's End achievements: You'll need an additional 48 for A Mask for All Occasions, bringing it to around ~371.
• One of everything from the vendors: 1172  Tricky Treat: 12 wands, 4 types of candy, Tooth Pick, 4 pets,  Magic Broom,  Hallowed Helm,  Little Wickerman, 24 playable race masks, 8 non-playable race masks.

You can acquire 4-6  Tricky Treat inside  Loot-Filled Pumpkin, which can be run daily. Averaging 5  Tricky Treat in the bag, you can get ~75 with 15 days.

You can complete several daily quests, listed below, for 12  Tricky Treat daily or 156 with 15 days.

You can acquire 1-3  Tricky Treat inside  Handful of Treats which is a reward from every single Candy Bucket. Each faction has over 120 Candy Buckets, so assuming 2  Tricky Treat, you will get +240  Tricky Treat from looting all the buckets.

This isn't enough to buy every single item for fun, but if you are just doing this on one character, you can comfortably get all the items needed for Hallowed Be Thy Name--also keep in mind several items can be obtained through alternate means, like the Headless Horseman.

You can also run the event on alts for the remaining battle pets and Toy, as these items are account-wide when learned.

Candy Buckets

Seasonal, pumpkin-shaped Candy Buckets are located inside every inn, near the Innkeeper. Each bucket offers a one-time quest that can be completed and rewards a small sum of gold and a  Handful of Treats, which contains 1-3  Tricky Treat and then has a chance to have other items such as masks and snacks. These snacks include  Pyroblast Cinnamon Ball,  G.N.E.R.D.S.,  Chewy Fel Taffy, and  Soothing Spearmint Candy.

You can also get Trick debuffs: Bat, Cat, Frog, Mini-Diablo, Snake and Wisp.

Visiting all friendly inn buckets on continent will reward an achievement. There is one for Pandaria too.