I have Camelback plastic one I love, and they make stainless now. It has a flip top sippy straw you have to bite to get flowing which prevents spills, and it has a loop for a carabiner. I love the one I got that has a narrower base so it fits in my cup holder. I love their bite system, and have it for my backpacking packs as well as a smaller one for when I'm doing outside work, and just for my daily water drinking because of the spill factor on my desk or in a bag.
The stainless ones are smaller than 40oz though, but I love the design on the drinking mechanism, so I'm biased. You could get him the back pack or shirt to wear so he can have it on while gaming
