How would you describe the game to someone who's not a hardcore FPS fan, why is it going to rock their world and have them running to upgrade their office PC to play it?
We've shown Half-Life 2 to a number of very casual or "so casual they don't" gamers. The characters and the world interactivity seems to be the key for them. Usually they tell us "it looks just like a movie, except I'll be in it", and we grit our teeth and say "Interactive Movie" is a Really Bad Thing, and they are not to say it again, or we'll take away their Half-Life 2 hat.

It seems like guns alone won't be enough - what else can you use to survive?
I was showing some people down in Hollywood the game last week, and was going through zombie town, showing how I could "Rambo" my way through with guns a-blazin, or I could "MacGyver" my way through by paying attention to the world and being clever (it's easier to be clever when you helped design the level, of course). We're trying pretty hard to reward people for thinking about what's in front of them and the tools the world gives them that could be useful.