Why him? Something of a media darling, Gunman Clive's games have delighted young and old alike. I don't know.
How would he fight? This is super difficult, because all Clive has is his gun and his hat. I'll get back to you on what his melee attacks are... maybe he uses Chieftain Bob's spear? (stop sniggering at the back!) His Final Smash, though, might be trampling everyone in range on the back of a marauding panda.