Some of my favorite memories:
DD bard- just for fun, taking all my thf/war/sam gear that was equippable on brd (along with my 8 dagger merits) into a burn party. I pulled, did song rotation, and DD'd and we kept constant chains. It was hilarious to watch people O.o when I popped out 1-1.5k eviscerations onto unsuspecting colibri.
4-man hakutaku- At 75, our setup was 2 sam/nin tanks (yes, you read that right), a rdm/blm and I think a whm/blm. The most hilarious part was us sam's resorting to Tachi:Hobaku to try and help with stun rotations. It actually worked incredibly well. Both of us sam's were evenly geared so hate would just kinda bounce back and forth. It got dicey near the end once everyone had basically capped their hate and he started trying to attack the mages, but still a grand ol' time.
Double E-body Nidhogg- He popped at like 2am, and we claimed him with only 5 people. By the time he died, we only had 8 and I think we were about 1 minute from him going enraged. We hadn't even really been seriously camping him, so when double ebody dropped and the second went to me, I nearly crapped my pants.
Soloing XXX on Thf- I loved soloing on thief. Some of my favorite fights were Charybdis, Aquarius, Zoral Jaa, Ose, etc.
Divine Might- We beat it the old fashioned way, before zergs and blm burns. I solo kited one of them. We wiped the first time to the ninja mijin gakure taking out 2/3 of the alliance, so the second time I hung back. It wiped out all but myself and one other dude with the ninja at like 10%. So I popped everything I had, SA>WS> I wing > WS... win. I was the only one left standing, it was pretty epic.