Magikarp for top tier.
-Availability:Can be found in any place of water with the old rod.
-Stats:10 base attack and 80 base speed? Sweet jesus.
-Moves:It's so good, it doesn't need to learn TMs.
-Power: Dominates wild pokemon like no tomorrow.
-Type: Only has two weaknesses and resists 4 types.
-Match-ups: Even Whitney's Milktank can't withstand it's horrific attacks.
Nah, here's my real suggestion.
Misdreavus for bottom tier
-Availability: Very rare, only found in Mt.Silver at night.
-Stats: The stats distribution is balanced, but it's still poor.
-Moves: It learns two attacking moves throughout it's entire life of leveling up, and only 8 total from leveling up. It can't really put good TMs to use either besides maybe Psychic.
-Power:Not very strong at all.
-Type: Shadow Ball isn't special(Who ever thought this should be shot, by the way) and it doesn't really learn any other decent ghost moves. It resists and is immune to a few things.
-Match-ups:Maybe against Whitney, but that's about it.
DISCLAIMER:Pokenoob here, things may not be entirely accurate.