Space Hulk is a clever boardgame of nasty, quick aliens versus slower Space Marines in the confines of a floating, derelict spacecraft. The original game, which I own, is a substantial, well-produced affair with glossy card tiles that interlock to make maps of the hulk's tunnels, as well as a set of plastic Space Marines and a double handful of plastic Genestealers -- the aliens.
This is a big game.
However, several people have had the idea of using GW's 6mm epic-scale miniatures and magnets to make a "travel" version of Space Hulk.
Andy Skinner's Travel Space Hulk
Leon Samadi's take with images of tiles
A complete set stuck to a refrigerator
I do have unbased epic Space Marines I could use, but no free Tyranids. I think, however, that I'd like to try making this with counters instead of miniatures -- I'd just print a counter sheet, back it with a magnetic sheet, and holepunch the counters. This means I wouldn't have to sacrifice any of my epic minis and I could have more visual variety. I'd also probably just produce the maps by scanning the maps as shown in the scenarios, then reducing them and reprinting them.