I joined when I first modded my DSi. I saw that GBAtemp kept appearing when I'd google stuff and decided to join. (to be completely honest, I thought it'd make me look cool. I'm cringing at that.)
My best memory... Hm... I loved the time when everyone was spam liking @ PineappleGod's posts, but I also just liked talking with a few people in PMs.
For my worst memory, @Nobody_Important4u getting banned. See, at that time he was still in my friend circle. We knew at that time that he was at a really low point and we were afraid that every little thing would push him over the edge. Hearing that made me very concerned. Though there was also a "yay he's gone from the temp" part to it too.