As part of the Winter Veil activities, players are given many gifts by Great-father Winter. Many of these gifts arrive by mail (which means, I guess, that trial account players miss out until they register).
One such gift is that of the Winter Veil Disguise Kit which I believe came to me as a result of having taken down The Abominable Greench in Alterac Mountains (you can see where to find him and what quests are associated with him through this link here).
I took the Greench down on the 15th, the first day of the festival, and so this was from my second day of gifts from Great-father Winter after that had been completed.
I think I'll save mine for July, especially since in the process of doing the quests for Great-father Winter, I also got a copy of the SnowMaster 9000
Devices
Requires Engineering (190)
Use: Allows an experienced engineer to turn water into a snowball. The Snowmaster requires a day to build up enough chill to freeze another snowball.
Item display is courtesy world of warcraft.allakhazam.com. ',VAUTO,HAUTO,FULLHTML);" onmouseout="return nd();">SnowMaster 9000 and can make a snowball in the middle of summer!