*** WARNING: MANGA SPOILERS ***
Majin Buu - 600,000,000
Super Gohan 2 - 250,000,000
Dabura - 170,000,000 (Injured)
Kaioshin - 45,000,000
Majin Vegeta - 360,000,000
Majin Vegeta [Final Explosion] - 800,000,000
Super Goku 3 - 1,080,000,000
Majin Buu - 850,000,000
Gotenks - 400,000,000
Majin Buu - 1,000,000,000
Super Gotenks - 1,200,000,000
Fusion
Evil Buu - 720,000,000
Mister Buu - 400,000,000
Super Buu - 4,000,000,000
Gotenks - 500,000,000
Super Gotenks - 1,500,000,000
Super Gotenks 3 - 4,500,000,000
Son Gohan - 5,200,000,000
Super Buu Gotenks - 6,000,000,000
Super Buu Piccolo - 4,050,000,000
Super Buu Gohan - 6,700,000,000
Vegito - 26,000,000,000
Evil Kid Buu
Super Buu - 4,000,000,000
Buff Buu - 4,600,000,000
Kid Buu - 720,000,000
Super Goku 3 - 720,000,000
Super Vegeta 2 - 280,000,000
Mister Buu - 400,000,000
Genki Dama - 22,000,000,000
Son Goku - 90,000,000
Uub - 12 (Relaxed)
Uub - 85,000,000 (Enraged)
So, there you go. Mystic Gohan is the most powerful non-fused character, Vegito could crush him (though don't know if that is Super Vegito or just Vegito, but does it matter?).
Doink!