I was wondering is it possible to import character rigs from a game and use them? For example, WoW has a lot of character emotes, is it possible to copy/paste those onto a blank model and have it emote accordingly?

Yes it is possible (allthough its a bit more work than simply copy & paste), (it would most likely violate the license terms of whatever game it is you are taking the rigs from though, the games that have permissive licenses tend to make their assets easy to access and use)