OpenOffice.org is a decent replacement for Excel, but let's face it, it's kind of boring.

To spice things up a little bit, go to cell A1 and put in the value

=GAME("StarWars")

Then hit Enter. You'll get this

Pick your ship, dismiss the message (or read it if you can read German)

Then try to shoot down the ships. You use the mouse to aim and fire.

Okay, so the game's not all that good, but it could probably kill a lunch break if you really stretched it out.

Oh, and the game is cross-platform, too.