UBRS / Strat runs were raids back then so id obviously say them
first proper guild raid was ofcourse Molten Core. No voice comms, a online DKP database and making everyone update CTRA to the exact same one and the first pack of molten giants followed by (if you were unlucky) 2 Fire Elementals was a darn nightmare
Oh, and "INNERVATE THE PRIEST" was really annoying
First raid was MC back in Vanilla was a lot different than raiding now. I remember having to stock up on bandages because DPS did not get healed at all. I don't count UBRs and Strat I am counting 40 man raids.
Molten Core, on my brother's account though, and it was in early TBC, only reason I had a chance at entering it by that time. Was such a Molten Core-fanboy back then, oh god was I hyped, that was until I found out how bad I was at tanking and ended up being kicked. Good times.