Titanium

I've used titanium in a number of my bots and like the material a lot. It's about as strong as steel, but substantially lighter.

I've found titanium as thin as .016" (yes, .016") can withstand a surprising amount of punishment in antweight combat. It is a very resilient material.

It's hard to make direct comparisons - but I would say that .016" inch Titanium provides a similar amount of armament as .06" Lexan does.

Thanks to a fellow robot builder, I've recently learned that titanium may be cut with a band-saw. The trick is to let it heat up a bit, until it sparks. After that, cutting is actually not all that difficult. I've done this with up to .07" thick pieces. It will however, destroy your blade fairly quickly.

Titanium is less prone to cracking than Lexan, and is a better material for parts that get a lot of abuse like weapon motor mounts.

7075-T6 aluminum may be a good alternative to Titanium for many applications. It has a similar strength to weight ratio, and is less expensive. Many aircraft applications utilize Titanium not so much for its strength, but its superior properties at high temperatures.

Titanium can be easily bent if heated with a propane torch.

Titanium was once a regulated material - and difficult to obtain. Now it's only moderately expensive and can easily be purchased online.

The vast majority of available Titanium is the alloy 6AL-4V - so picking the right stuff is easier than with other metals.

Titanium Joe is a great place to buy small orders of scrap Titanium.