I brew a CDA year round since that's my wife's favorite and the beer I've made the most of and have really dialed in.
This year I'm planning to re-try a brew I made a couple years ago that went horribly wrong, an Imperial Milk Stout with Cocoa nibs called "Waiting for Santa".. the inspiration was a beer to leave with cookies instead of milk. I got too ambitious with a high gravity beer too early in my homebrewing career and met with disaster, but now I'm ready to re-try it.
Each winter I brew a Belgian dark strong that I bottle condition for nearly a year, so it comes out in late summer the following year. Besides that I don't do a lot of winter specific beers, but now this thread has the ideas bubbling..