FPS demo to stress a system?

[Helium_Junkie]

I'm building a PC for someone and would like a high end game to download and try on it, to see how it handles. Would anyone have a recommendation of a currently quite demanding demo?

Many thanks.

 

[Dicehunter]

crysis single player demo, everything on max.

 

[KNiVES]

Seconding Crysis demo. It runs worse than the retail game too.