Falco (SG/N) - Falco is a sharp lookin' guy even more so than Fox. He acts like a human, lives like a human and most likely would take showers like a human. I don't hear much about smelly birds. He's a pilot and he doesn't usually do anything other than fly.
Link (S/N) - As much as I love this guy, I'd have to say that he'd lean more towards stink. He's always roaming around the woods to save Zelda. This could take days, weeks even. And it wouldn't make much sense for him to simply stop for a shower. He rolls to dirt, grass, climbs trees, horse, smoke,... magic, he must be the most bloody in the game all from so many different monsters including his own. And considering that his adventures are years apart, he can't be that bad. Also his hair is always perfect. I can understand Ike and Marth, they only go through formal combat, regardless they do it every day of their lives... >_>
Samus (N) - The only one I'm completely sure about. xD Machines don't usually give off a distinct smell. Underneath the suit she would most likely be really sweaty, but that has everything to do with Zamus and nothing to do with Samus. Sure she'd get hit by blood here and there but all that can just wash of in the next swamp she jumps in.