Robots: WoW Battle Pets

Vendor: World Vendors

Cost: 50 (unlimited supply)

Vendor: Paul North

Zone: Orgrimmar

Cost: 30 (unlimited supply)

Vendor: Quackenbush

Zone: Stormwind City

Cost: 30 (unlimited supply)

Profession: Archaeology - Dwarf

Artifact: [Clockwork Gnome]

World Event: Feast of Winter Veil

Quest: You're a Mean One...(Alliance)/(Horde)

Approximate Drop Rate: 1 in 65 dropped (available 14 days per year)

Trading Card Game: Worldbreaker

Profession: Engineering [205]

Taught By: [Schematic: Lil' Smoky]

Pet Store 

Drop: The Curator [??+]

Zone: Karazhan

Approximate Drop Rate: unknown

Promotion: StarCraft II: Wings of Liberty Collector's Edition

Profession: Engineering [475]

Taught By: Goblin Engineering Trainers

Drop: Void Reaver [??+]

Zone: Tempest Keep

Approximate Drop Rate: unknown

Drop: Dark Animus [??+]

Zone: Throne of Thunder

Approximate Drop Rate: unknown

Drop: Haywire Sunreaver Construct [92+]

Zone: Isle of Thunder

Approximate Drop Rate: 1 in 5

Pet Battle: [3-4] Westfall

Promotion: Mountain Dew Promotion (Summer 2009)

Vendor: World Vendors

Cost: 50 (unlimited supply)