My biggest trigger is always some guy.
Whenever I have only the slightest little feeling for someone I barely know the roller coaster is on. Beside from that, offcourse: Sex, seeing my dad playing with my little sister, people around me having an argument, my mum not picking up her phone, eating sounds, people criticizing anything about my looks, comments about my personality by someone who is close to me, not being part of the group, too little attention, too much attention (depending on the mood) and people responding short to anything I say... And obviously alcohol makes all of it a lot worse :-).