I can't really say I have a signature pokémon, since i tend to use whatever i can in that specific game, but if I had to associate myself with one, I'd pretty much say Zangoose or NIdoking. Yup.
Nidoking was what I may call "my first love", since it was the one that helped me (as a Nidoran) pass Brock's gym in pokemon Yellow, thanks to his Double Kick. I started to like him ever since. As for Zangoose...dunno, i just like him. I still haven't gotten one on Reborn, but I will, indeed.