Well it's safe to say that if Shaquille had played more he would be the easy leader, but spotting Dwight Howard an extra twenty games played has allowed Dwight to emerge as the NBA's #1 dunker.
Now that's going by sheer quantity, without "style points" considerations and there's several other fine players in the top five, including Marion (who gets a lot on Alley Oops as we pointed out here), Carmelo, and Wade.
Leaders in Dunk FG% (min 50 made)
.985 Childress
.984 Haywood
.975 Gadzuric
.974 Mourning
.968 Josh Smith
Worst dunkers in percentage (min 40 Att)
.788 Dampier
.800 Darius Miles
.810 Rasheed Wallace
.825 Petro
.827 Richard Jefferson
Highest Assisted % (min 40 made)
95% Haslem
93% Ilgauskas
92% Deng
91% Stevenson, Biendrins
Lowest Assisted % (min 40 made)
52% Pierce
53% Gerald Wallace
56% Vince Carter
Highest % getting dunks blocked (min 40 att)
11% Marvin Williams
9% Haslem
9% Krstic
8% Przybilla
Lowest % getting dunks blocked (min 40 att)
0% Marion (181 Att)
0% Anthony (155)
0% Garnett (92)
0% Bosh (80)
0% Jason Richardson (78)
Dunks per game
3.39 - Shaquille O'Neal
2.61 - Dwight Howard
2.40 - Marion
2.14 - Anthony
2.05 - Wade
Minutes per Dunk
Shaq -- a made dunk every 8.9 minutes!