This poll isn't accurate. The SSC Elevator boss isn't on the list.
Lightninghoof - US : @WoWNivan
Imperial Vizier, Omnitron Defense System, Flame Leviathan & Razorgore the untamed were the best imo.
Voted Razorgore.
Razorgore the Untamed x10!!!
I enjoy raiding MC but when BWL came out this fight was like nothing i'd ever seem before. I played a shaman and for every single fight...well over(besides being an ooc rez'er) this was the first fight I truly got to shine. Dropping earthbind and kiting while picking up adds and running for my life was fun as hell.
This fight might be why I'm still raiding to this day. It took something I kinda liked and made it an unforgettable experience which I always come back to(raiding)
A few people have said that High King Maulgar shouldn't qualify as "entry level", but he absolutely does. Making the jump from 10 man to your first 25 man raid in TBC was a big thing, and Maulgar was what would make or break that. It was a fight that put strong emphasis on raid coordination, tank and healer roles, dps order, where to stand, where not to stand and how to correctly pull a boss. In fact most people would probably go as far as saying that the pull was probably the hardest part of the fight.
He was not a gear check in any way, and could easily be done in full greens, he was purely a test of the ability of the raid to coordinate and work as a team (see Gruul for your gear check), and downing him will be remembered as a significant milestone for many guilds who had been stuck in Kara for a long time, and the start of 25 man progression. He also dropped some good loot, Tier 4 shoulders held a certain ego value about them that screamed out "I raid 25 mans".
So as far as entry level goes, he wins hands down for me.
I have no clue why Marrowgar is getting so many votes. As for me, I'd vote the following three to be my favorite in order. I voted the first two mostly because back when they first came out, they actually took some time and work to beat. Nowadays, every intro boss is completely faceroll.
1) Kalecgos
2) Hydross
3) Omnitron
It's like fighting Ozzy Osbourn. With Eeyore's voice.
You either die a Varian, or live long enough to see yourself become a Thrall...