I have seen a tool that helps drain the last of the fuel out of your isobutane fuel canister, and then pierce it to make it easy to crush. It's a simple little gadget that looks like a can opener. What is this tool called and/or where can I buy it online?
Cheaper and easier solution.
Attach your stove thingy (In my case, a pocket rocket). Open all the way and invert the can (away from flame sources obviously).
Use a cheap and old fashioned church key to puncture the side.
Total cost, approx. $0.50.