I fell in love with GTS soon after I got Pearl. Two of my silly Pearl projects involved generous trades ... I would catch Pikachus and offer them for Bidoofs, and even sillier, I would search for Bidoofs and trade for them in order to collect lots of other people's Bidoofs.
In White I was using the GTS extensively, and a lot of players were asking for starters of course, so I always kept a big supply of hatched starters. And from time to time if I didn't have another trade I wanted to ask for I'd put up a starter for a Patrat. However in gen 5 I just release the Patrats :(
More recently I've gotten heavily into putting up Dream World ability pokemon for Patrats, just because I can. First I put up mostly Bidoofs, now I put up mostly Vulpixes. (As for the Bidoofs) It's fun to help fill the world with banned Pokemon :P
And once someone TOTALLY upstaged me ... for a Snivy they sent me a legit-seeming shiny Patrat!!