I'd say they should've never invented Chansey. It just doesn't look like the concept of a Pokemon. Its just a fat blobby....THING. And to boot its too much used (well, its evo is).
Others I'd say:
Licky line - Seriously, they are ridiculous.
Luvdisc - No comment needed
Rhyperior wasn't needed. Sandslash deserved the evo more
Dusknoir - see above, replace Sandslash with Banette
Bibarel - Normal/Water is fun, yet ANOTHER early game rodent like thing isn't.
Furret - Most useless of the early rodent family.
Finneon/Lumineon - We have Seaking already. Worthless poke.