Gravitation was pretty much the series that made me a yaoi fangirl and the first ever series that had me squeeing (well, the latter half of the manga did kind of sour me, but I still love Yuki/Shuichi). Unfortunately, I entered the fandom long past its prime, but I was still able to hunt down a ridiculous number of fantastic fanfics. Oh my god, just typing this is reinvigorating my love for them. <3

I do have to admit that Dee/Ryo of FAKE ranks a very, very close second to them, though. (And am I the only one who even knows what Kento/Akira is? Or desperately wishes that they could have had more than 2 volumes to be adorable and hilarious?)