Anything that constantly uses paralize, sleep, sting etc...
I got lost in a cave and constant pokemon sleeping, paralizing and sting.. I stock up on about 20 potions for each thing (like 20 paralize, 20 sting and 20 sleep.. as well as ice and burn heal and everything) and in the end i had all my burn and ice heal, But 3 paralize heals, 0 sting heals, 7 sleep heals :/
Stupid zubats, bronzors etc..