Okay, this is monstrously stupid, but I just happened upon this the other day, and had never seen it before.
Step 1: Start!
First, yank the pull tab off a can of Red Bull.
(Look, I'm telling you, I know this is stupid. But it's also kinda cool.)
See that cutout? Looks like a bull, right? charging to the right? Neat.
What you do now is take your fingernail, stick it into the curve of the bull's tail, and pull that tiny flap of aluminum back.
Here comes the magic!
Step 2: Ta-daa!
Now THIS is going to BLOW YOUR MIND.
Once you've bent that aluminum tab back? It's A CAT facing to the LEFT!
That is all.