The one where they're coming out of the goddamn walls, man

This amazing browser game ports the obscure Aliens boardgame tie-in to your PC, complete with the film's rousing score, all the weapon sound effects and Vazquez bellowing "Let's ROCK!". It's awesome. And, also, awesomely hard.

With just three missions, you might not expect much time-killing capability. But each episode is more challenging than an arm wrestling match with Vishnu, as your rag-tag band of colonial marines (plus Ripley, Newt and Burke) are all too swiftly surrounded and outnumbered by the razor-fingered xenomorphs.

We played this until every move the Aliens made caused us to shiver. Until each trooper that died was a hero - and a far sight better off than the ones hauled to the hatching chambers as unwilling hosts. Until our boss demanded we explain what we'd been up to for the last six hours. Maybe it's too good.

The one where leaving the house is an achievement

The Hitchhiker's Guide to the Galaxy game is probably the most ridiculous, confusing, complex and brilliant game you'll ever play. You begin as Arthur Dent, waking in his bedroom with an apocalyptic hangover. Which happens to be fitting, since today is the end of the world.

It's a devious but intelligently made text adventure, and excruciatingly difficult. It's likely that most people won't even manage to leave Arthur's bedroom (before it's bulldozed into ruins) let alone the house. We once managed to re-enact Arthur's classic moment lying in front of the bulldozer. But we can't remember how. Good luck!