Titanium.
Doesn't rust, needs no paint to leave behind on the parking rack, scratches buff out with a Scotch Brite pad.
Heavenly ride too.
indeed. i voted for aluminum in the poll just to agitate slimrider (
), but titanium really is a sublime material for an everyday lightweight but strong bike. the only negative to titanium is cost. it's a pity it's so expensive, precluding it from becoming the material of choice for bike frames for the masses.