Since Shounen-ai/Yaoi is my most favorite genre ever I'm gonna add few animes that I love most.
1. Junjou Romantica (seasons 1 and 2)
The best Shounen-ai anime ever! It has romance, comedy, love triangles and sooo much more. Saw it five times already and I want more!
2. Sekai-ichi Hatsukoi TV (seasons 1 and 2)
I gues it goes without saying why I love this one - its plot is basically Junjou Romantica's plot branch. The characters are very similar and you can even see Usami Akihiko's past in here!