I go for 12" balloons mostly - a good compromise in looking good, and not taking too long to blow up. Starting to like 260Qs as a form of bondage. Yum yum
Anything that's big from around 16 inch to 36 inch. Some of my favourites are the GL airships, South American 24's, those big soft delicate 24 inch balloons (I think they might be Chinese), and 17 inch Gayla's.