Hmm..probably any really.
I personally wouldn't mind a lil Bulbasaur, since I probably wouldn't fit much anyways, it wouldn't really evolve much.
yet on the other hand Cyndaquil are adorable too <33 so are Fennekin ;w;
and Squirtle and Oshawott are of course adorbs too!
So really, I don't have much of a preference...just any of those really |D