I watch pretty much a bit of everything... But I mostly like Shounen... lots of action and humour is good.
I'm also partial to Shounen-ai and Yaoi. It depends on my mood.
shonen is actually a demographic, not a genre. and it's not all action. heck, believe it or not, Inu X Boku S.S. is a shonen. conversely you have stuff like Saiyuki, which while the first part of the manga was released in a shonen magazine, all the rest was released in a shojo magazine.
also, do you mean actual shonen-ai, as in, the genre specific to the 70's and 80's, or Boy's Love (also known as BL or Boizu Rabu) which is a genre that began in the 90's and is still going today?
I love all anime genres, but I'd have to say that the Mecha genre really stands out for me. It's basically filled with bits of everything, from politics, romance and even harem. Also anime that spand past your regular 13-26 episodes, like Naruto,Bleach,One Piece, Soul Eater etc.
i don't like any kind of harem because i find it annoying, same with ecchi, i can stand an anime with a little of it but not ones that are made up entirely of it with little storyline. it gets old fast. though high school of the dead was one ecchi that i actually liked.