Togekiss

The last evolution of Togepi added in Generation 4. It will make you want to throw your DS out of the window with Air Slash, Serene Grace, and a King's Rock. You'll be lucky if your Pokemon doesn't flinch from its attacks. If you see one, make sure to use your fastest Pokemon or you won't be able to do shit.

Trainer 1: I gave my Togetic a Shiny Stone and it evolved into Togekiss.
Trainer 2: Don't you dare use that Air Slash bullshit on my team.