Do you have access cards with the magnetic stripe at your business? This is a very simple and quick prank thats really funny too.
Step 1: The Tape...
All you need is tape and access to your workers key card, which might be tricky in some situations.
Just tape over the magnetic stripe and push out all the air bubbles and you're done! My dad tried it at his work and his friend was getting really angry at the machine for denying it all the time. Be sure to let them in on the joke before their head explodes! That would be bad. = )