When I first saw the Unova starters, I was having a hard time choosing, but was leaning towards Snivy. It would have been the first time I started with the Grass starter in my first game of a Generation. (The only time I've used a Grass starter was in Red, which I got after I beat Blue. I evolved Bulbasaur into Ivysaur and kept it that way all the way to Lv.100, since I loved its sprite.)
When their evolutions were leaked (their Sugimori art, not those small images), Daikenki really impressed me. So, for the third Generation in a row, I'll be starting with the Water starter in my first game of the Generation (Black). It's going to be hard for me to use Daikenki, though, because there are so many cool options for an in-game moveset. xD
Once I get tired of Black and want to move on to White, I may start with Snivy. However, I'll be starting with Oshawott for sure in Gray / whatever the third game is.