Yup, a medium raw shrimp from the grocery store. The decomposing shrimp will provide ammonia to cycle the tank.
Have fun with it, go into the grocery store and ask for "one medium shrimp", then mumble about how hungry you are as the seafood guy looks at you like you're crazy.
It also helps a lot if you can get a bit of rubble or sand from an exiting, healthy tank. This will import the needed bacteria and that will speed things up a lot. It can take quite a while to cycle if you don't seed with bacteria.