I would suggest Mudkip, because its a strong water pokemon and when its in stage 2 and 3 its unstopable(unless theres a grass type).These are some of its strong and weak points.

Fire-unstopable
Water-fair
eletric-unstopable
grass-no chance
Ice-fair

Recommended moves:

Muddy Water-Fire,Ground,Rock
Brick Break-Rock,Ice,Dark,normal,
Earthquack-Rock,posin,Fire,electric
Ice Beam-ground,flying,Dragon