Tympole, Palpitoad, and Woobat. God, their designs are just hideous and weird. Woobat's nose is in the shape of a heart, for god's sake! Tympole and Palpitoad look seriously ugly as well. Good thing Seismitoad (or however you spell it) looks cool.
Tentacool and Zubat are just plain obnoxious in the ocean and caves, respectively. For some odd reason, Tentacool still appear even when I use a Repel.