Which Pokémon Would be Better as a Single Type?

Pokémon come in all sorts of type combinations, but every now and again there's a prefect storm of a type combination having awful matchups, and the Pokémon's design and lore not even really supporting two types... It's in these cases that said Pokémon would be better off being a single type, so let's check out which options might be improved by shaving off some of the excess baggage...