Here are my (apparently) favorites:
10. Thundurus (pretty cool, but not top 10- should be Rayquaza)
9. Hitmonlee (he can kick you in the back of your face!)
8. Dusknoir (not only does he steal souls, he does it with a giant fanged jaw!)
7. Conkeldurr (not sure how he got here, should be Infernape)
6. Mewtwo (the original uber)
5. Gengar (this O.G. (original ghost) is awesome, but Haunter is more awesome)
4. Metagross (like a tank, supercomputer, and another awesome thing combined)
3. Latias (so serene... so graceful... should be lower)
2. Heatran (everyone's favorite volcanic toad)
1. Nidoking! All hail the horned one!