Platinum is a good alternative to white gold in that it is a little stronger and since it is pure instead of being an alloy, you are less likely to develop reactions to it. Titanium, Tungsten, and stainless steel are all good option especially if you do much work with tools and heavy equipment. Tungsten is hard to cut but as has been mentioned, it is brittle (it is basically iron). So in an emergency they would probably have to put it on a hard surface and hit it with a hammer.
The option I have is a ceramic ring. Like with tungsten, it is hard but brittle. It just isn't as tough to break as tungsten. Neither can be sized so you have to order the correct size. In my case it is a black band with a stainless insert. This is a link to it. http://www.fredmeyerjewelers.com/Products/Black_Ceramic_and_Stainless_Steel_Ring--1274042.aspx