7th Gen?  That’s actually really hard.  There are a lot of really cool and great Pokemon this gen, and there hasn’t been one that I’ve used that I haven’t loved.  Primarina and Salazzle are favorites, because usability and furry bait, but I also love Araquanid, Mudsdale, Vikavolt, Kommo-o, Tsareena, Mareanie, etc.