Two parts of one odd conversation at work: if humans had teeth like sharks, or had tails like dogs, life would be pretty different. For one thing, if your teeth are always growing back, why bother protecting them with a mouthguard? Furthermore, some people would get their teeth engraved to show pictures, their initials or other things before they fell out and were replaced. If humans had tails, then chairs, pants, toilets and a lot of other things would be subtly different too. I imagine the options for toilets would come down to repositioning the cistern or having squat toilets everywhere. Chairs would probably all come with holes or splits in the back, and pants would tend to be worn much lower around the hips.
Mokalus of Borg
PS - Personally, I've wondered what it would be like to have two thumbs and three fingers on each hand.
PPS - I expect it would make for a pretty strong handshake.