Not that I'm suggesting you try it out, naturally. But if you had to ensure something - or someone - slept for a very long time with the fishes, Modder D. Heiße's concrete PC mod is heavy enough to do the job.
Made from a single layer of concrete, Heiße wrapped it around plexiglass windows, welding rods and steel sheets, to keep the computer internals safe and secure. The whole design is quite stylised, and if you look over at his tutorial on The Best Case Scenario's forums, you can see a lot of attention to detail went into the creation. It definitely wouldn't look out of place next to a Cinema Display, that's for sure. [The Best Case Scenario via Technabob]