The best dunk I've ever seen in the LNC, bar none, was by Jason Detrick against Central Connecticut State in the first game of the 2002 season. He drove the baseline and threw it down over the top of some poor dude with EXTREME prejudice. It was gorgeous.
The second best dunk is the first full play you see on the '88 highlight tape. King blocks a shot and rifles the carom, one-handed, up the floor to Blaylock. Blaylock corrals the ball behind his back, I **** you not, and kinda flicks it to his left hand. Once under control, he feeds it to a streaking Tony Martin who's roaring into the lane. Some clown from Missouri tries to take a charge and gets totally tea-bagged. Full blown destruction. You get a glance at the OU bench as Martin does the cabbage patch above the poor Mizzou clown and you can see the whole group has formed some sort of patchwork conga line in celebration of the dunk (assistants included). You've got to see it. It's fantastic.
The best dunkers:
Calvin Pierce
Shawn Clark
Andre Wiley
Mike Bell
Angelo Hamilton
Taylor Griffin
Blake Griffin