Avid SAAGO stems were pretty cool. They use a funky top cap bolt down expander wedge thingy with 3 bolts. Another similar setup was also used by Sweet Parts stems (if you're into tubular steel that is) super clean look, no bolts on the sides anywhere.
A.R.T or ART did them too - I've a 1" on my track bike with bolts to the front, well, side, tucked out of the way. Ebay purchase for £13 new not that long ago, cheap, light, no unsightly bolts.