The first time I played it, I chose Torchic, which is unusual, since I rarely take the fire starter in my first play through. I chose it for the simple reason that it was the cutest out of the three. I ended up regretting it when it evolved, because Blaziken is pretty ugly in my opinion.
Nowadays I prefer Treecko, although mostly for sentimental reasons and because Grovyle is cool. Mudkip is alright I guess, but eh. I never really used it much.