Hack Of The Night : How to open a can of tuna without a can opener

I'm sure you'll never find yourself in this situation, but lets just pretend.  For some reason, you're stuck outside with only a can of tuna for nourishment, but you don't have a way to get into it.  Lets say this particular can of tuna doesn't have one of those pull tab things, and you need  a can opener to get into it.  Again, I realize this will probably never happen, but let's say you're playing caveman with your bestie, and for some reason you have cans of tuna.  This is getting weird, let's just get to the hack...