This is my top ten list, please post it.
 
10. Nidoking - very few people give this pokemon the credit it deserves, toxic is one of the best moves there is.
9. electabuzz - many people disagree but I think this pokemon is worn out, there has got to be some replacement for it.
8. ninetales - this pokemon is very powerful lure is a built in GOW and fireblast incinerates just about everything but ER or SER will absolutely destroy this pokemon
7. alakazam - this pokemon's pokemon power is great have a Mr. Mime active and you nearly have perpetual motion.
6. Raichu (base) - again many people disagree but agility is one of the greatest moves ever!  you have a 50/50 chance of being invincible.
5. moltres - this pokemon is the ultimate decker!  Slap on the energy then crush your opponents deck to a pulp, play this pokemon right and you will have decked your opponent in no time.
4. Mr. Mime - this pokemon should have 2nd maybe 1st place except for one minor detail... colorless pokemon.  Colorless pokemon eat him alive seeing as how almost all of the basic ones do twenty or less.  Have you seen what happens when Jigglypuff meets Mr. Mime.  Trust me if you like Mr. Mime you don't.
3. scyther - everyone knows why.
2. ditto - I know people are thinking yeah right! but have you looked closely at him, better yet played with him, ditto adds a whole new branch of strategy to the game.
 
And now the moment you've all been waiting for.
Drum roll please.
Duh
du, duuuuu
du, duuuuu
1. Muk! - yes believe it or not Muk!  I know your asking why so I will tell you... two words... get it now?... if you're very dense and don't get it yet... pokemon power!  Muk stops Mr. Mime and Rain Dance decks in there tracks.  Ever seen a Blastoise unable to dance trust me, it's funny!