"Vex in a Bucket" was the best screenshot I've ever seen - even better than The Division Queue.
Skyrim's backwards flying dragons made me laugh. Also, Mass Effect 3 had this one where whenever you entered Liara's room, Shep's head would be fixated on Glyph, during some moments, it looks like Shep is about to go all exorcist.
I never saw this in my game of Black Flag, but I really wish I had. It invokes a nightmarish Pirates of the Caribbean feel.
The Heavy Rain & Skyrim glitches had me laughing like an idiot.