Well I would choose Totodile, since it is a water Pokemon and is not extremely weak against Leaf Pokemon (As compared to Leaf against Fire and Fire against Water).
Well Blaziken would lose horribly against Feraligator (If I spelled both of them correct). And so will Meganium against Blaziken. So the easy choice is Totodile, as it would have a fighting chance against Meganium.
Thanks for correcting me, Typhlosion indeed.
I have played some these Pokemon games, Grass Pokemon are insensitive to some Water Pokemon attacks, but they always don't do great damage to the Water Pokemon. And this out of my experience in the games.