Torchic line! My first Pokémon ever was Torchic, and it worked very well for me. Combusken is a very useful Pokémon to have at that stage in game, and Blaziken just rocks in general.
Chimchar line never felt durable enough to me. Speedy, yes, but they couldn't really take hits.
Pokabu is cute, its evos are ugly. And fire/fighting is just bland by the time Isshu rolls around.