In World of Warcraft, we've generally been conditioned to do something because we get something in return. I know this is a huge generalization, but a lot of people now PVP because you can get some great gear from it. People raid because they want epics. Quests are done for rewards, etc. But sometimes it's fun to do something, just because.
I went with a fellow guildie or two on a raid of Orgrimmar of about 15 people or so the other night. As far as I could tell, there wasn't any real purpose in doing it, unless you count just hanging out and having fun. One of the paladins is fairly epic'ed out and was able to keep me (a low stam, clothie mage) alive as I tanked/Aoe'd everyone in sight. As long as we didn't get too may guards, we stayed alive and had a lot of fun. The funny thing was, about 5 people left, and it actually made the group stronger. Kinda odd, but funny. Eventually enough horde came in, and we had to escape out... somehow. The same pally provided a distraction for me as I rezzed and teleported.
I like to do a lot of things, just for the fun of it. There's the "silly" holiday quests, there's exploration/cliff diving for others... Personally I also like to fish, just to kill time and mess around. I don't really expect to make any major money off of fishing. (Currently a fishing skill of about 148 doesn't do much for the coffers.) I just do it for fun.
So, the question of the day is: What are some of the things that you do, or have done, in WoW just for the fun of it, that probably don't or won't net you any rewards?