My group traditionally runs a Memorial Day game of Space Hulk, and we had a good solid hulk that lasted about five years before it was defeated.  I and one of the other guys have taken it upon ourselves to design a bigger, badder scenario.  We've come up with a colony assault, sort of like Aliens.  We're adding different types of 'nids alongside Genestealers and Hybrids.  I'm interested in adding optional missions for the Marines, with small rewards for successful completion, as well as random events for each level of the colony.

Hence, I'm looking for suggestions for random events.

Examples:

Lights Out - The lights have failed across the entire level.  Line of sight is reduced to 10 squares.

Lockdown - The colony computer has sealed all doors throughout the level.  Doors must be destroyed to pass.

Others?

-Thornhammer

motion sensor malfunction.

Whenever a blip gets into ine of sight roll a dice.  On an odd number the blip disappears.  On an even number add that many extra blips

Colonists: A blip may be a colonist. make up a rule about accidentially shooting a colonist instead of a genestealer, as almost happened to newt in aliens. Lose points for killing colonists.

In homage to the movie Aliens (special edition directors cut never seen before bells & whistles edition) :
 
Sentry Gun : An automated sentry gun has been left here by colonists / previous assault team. Roll the dice, and on an odd role it fails to register your IFF transponder and opens fire on your squad.
 
Dangerous Ground : Flammable liquids have been spilt in this area. Gunfire within a 6 square radius has a 50% chance of setting off a fire. Flamethrowers will definately set off a fire.

Radiation Bath: Level is flooded with radiation that isn't deadly, but that interferes with electronic sensors, causing them to give erroneous readings.

Fuel dump: Tanks of flammable liquid are stored here. Shots towards this area might hit a tank and send it up in a large explosion. (treat as a flamer hit) May  be deliberately shot at. Each tank can recharge a flamer by one shot. (tanks should take up 1 space on the board)

Spawning pool: There's a pool full of Tyranid proteins in a bio-lab/agi-dome/atrium, it spawns small 'ripper' aliens each round once the marines are within X number of spaces. (Small, fast, but not as hard to kill as the genestealers) The pool can only be taken out by a flamer hit or large explosive.

Bio turrets: Stationary Tyranid growths, spit poisonous spikes at any non-Tyranid within 8 spaces. Found only near spawning pools or other areas of bio growth.

Gouts of steam or other vapor coming from old pipes.

Dangling cables coursing with electricity.

Scurrying rat-oids setting off sensors.  Maybe they could swarm and attack.  I doubt they could penetrate power armor but they might pin a guy down.