Mudkip is adorable. It always looks so happy and playful! The wide grin, the sparkling eyes. It's my favourite Hoenn starter. Maybe it's just 'cause I have an affinity with Water-types, but I usually start with it.
Water/Ground, which Mudkip becomes upon evolving, is also fantastic typing. A 4x Grass weakness is very workable, considering it has no other weaknesses. They're great STABs, too!