I say Vince's Fredric Weis dunk should have its own category -- there has never been another dunk even remotely like this. Blake Griffin, you clear a 7' man standing 4 feet from the basket and then we will talk.
The dunk I would put at #2 is Michael's against Ewing. He has basically zero momentum built up, has just spun by two guys and has all of one dribble to gather and dunk on a waiting Ewing. Awesome.
Some others of note:
LeBron from the free throw line in a game --
Shawn Kemp on Lister -- http://www.youtube.com/watch?v=T_PzNsUotVI
(note that Mullin chooses to not step in, undoubtedly worried that Shawn might have his first career assist to Chris’s man)
Baron on KG -- http://www.youtube.com/watch?v=r3bBvcJWcdU
(KG learned from that point forward,
every time an opponent was in the open court against him, KG would always bump
him around the free throw line and throw him off balance. I don’t remember a
young KG ever being dunked on again).
This is a nearly impossible dunk from a young KG, but it never got an pub’ -- http://www.youtube.com/watch?v=mzrRG8Oits0
You rebound a ball and do not gain control until it is waist level, yet you still dunk it. I have never seen anyone else do that.
I loved Chambers' dunk. Baron's dunk on Kirilenko is fantastic. Overrated -- Rose (basically an uncontested driving dunk), Iverson (a tip dunk you will see 40 times a season), Kobe (it is a charge -- if you simply looked the other way and didn't call charges, we would have 200 awesome dunks a year).