I generally avoid single-purpose tools, but after ruining a couple of tools puncturing MSR IsoPro canisters, I asked for a Snow Peak Kuwagata for my birthday. It makes a nice squarish hole with no fuss.

After puncturing:

I used to recommend using a “church key” can opener, but I bent our OXO church key. Then I tried the can opener on a 50+ year old stainless steel Scout knife. That really didn’t work. Dang, the MSR canisters are tough.

My relatives in Texas suggested shooting the canister with a .22, but that would likely not go over well in our suburban back yard. I’m also pretty sure it is against BSA shooting sports rules, even if done on a range. 🙂