GTA IV just keeps on giving. It's been out for a whole year and GamesRadar is still finding hours and hours of entertainment in little things. Like... pushing people down steps.
The Euphoria engine allows pedestrians to react realistically to forces from any direction. Which means a gentle nudge on the steps (or a less gentle thwack with a baseball bat) will send them tumbling arse over tit. It really shouldn't be as fun as it is but it kept them amused for ages. Especially when they say things like 'Aw, Hell, I don't need this!"