Aside from the standard gold and stainless steel, high-end watches are often made of platinum or titanium.

Platinum is a very heavy metal, and gives a shiny white metal appearance. Unlike gold, pure platinum is fairly hard and resistant to scratches (similar to hard stainless steel). For this reason, it is often used in 95% purity (i.e. Pt 950). However, raw platinum is more expensive to use, not only because of its rarity, but also because it is used in higher purities and requires more effort to work into a final shape.

Titanium is a relatively light-weight metal, with a hardness exceeding that of most steels. It also has a poor heat transfer capability, which means that it won't carry heat away from your skin as quickly as steel or aluminum (i.e. it will feel warmer to the touch - sometimes you'll see claims that titanium "remains at skin temperature" - this is technically incorrect, any more than a small piece of wood stays at skin temperature). Several varieties of titanium are available. Titanium has some interesting mechanical properties:  it can "rip" when cut so it is difficult to machine, and two pieces of titanium pressed together can "weld" themselves together. This latter property is why it is important that watches with titanium cases and backs have the casebacks removed periodically - the threads can actually rip out of the case if left undisturbed too long.