As a fanfiction writer, I generally write slash, but I have some het pairings I write for, too. Outside of fandom though, there's kind of a lot.

This is by far not a comprehensive list.
Air Gear: Agito/Ikki/Akito
Bleach: Renji/Ichigo (I only write a quarter of a fic for this though ahaha)
Black Cat: Train/Sven
Gundam Wing: Duo/Heero, Trowa/Quatre, Wufei/Sally, Wufei/Relena
Hikaru no Go: Touya/Shindou (...of course), Waya/Isumi
Fairy Tail: Gray/Natsu (THIS THIS THIS), Jellal/Erza (I HURT SO MUCH FOR THEM),
I also read a Team Natsu pileup - Erza/Natsu/Gray/Lucy which blew my mind and makes me wish there was more of this! Though Jellal trumps all and would either have to jin in or take Erza away if he ever got his shit together enough to be with her. XDD
FFIV: Edge/Rydia. Kain/Edge/Rydia (preferably in that order in bed XDDD) <--- Not anime but... >.>;
NANA: NOBU/HACHI SO MUCH OH MY GOD. COME BACK AI YAZAWA AND GIVE ME A HAPPY ENDING FOR THESE TWO. Also Ren/Nana *Cries forever* and how about Takumi/horrible painful death? (I hate him so much. SO MUCH. He raped Hachi, and if that wasn't enough to seal the deal - it was - the fact that he's a terrible person would have done it for me.)
Naruto: Once upon a time, I shipped Sasuke/Naruto. XDDD
I only listed things I either read fanfiction for regularly or write fanfiction for (or did so in the past sometime). If I tried to list all the pairings I root for, I'd die before I finished. >.>;