Tank! is the opening song for the anime series Cowboy Bebop. It was composed by Yoko Kanno, and played by The Seatbelts. It's a short, jazzy number, with just a few lines and a lot more instrumental.

I think it's time we blow this scene.
Get everybody and their stuff together.
Okay.
Three.
Two.
One.
Let's jam!

It's a very nice piece to listen to, and is a wonderful introduction to the music that is in Cowboy Bebop. The song is availible on the Cowboy Bebop album. There are also some remixes availible, Power of Kung-Food Remix on No Disc and Tank! - Luke Vibert Remix on the Music for Freelance album.