It's not realistic, but Zelda Wind Waker has one conveniently going in and out of the cell in the Forsaken Fortress 

wouldn't that be kid-sized vents ?

Syphon Filter 2 & 3 had them.

Not sure about the first one though :/

tenacious d and the pick of destiny:

youtube: storm the gates. Great song, man sized vents

Rogue Ops.  I'll look at my collection later to find some more.

BTW, none of that shit would fly in my high security facility.  We have hand scanners, microwave motion detectors, alarms on every device, motion detectors built into the ceilings, and tons of other stuff that I can't even talk about.  Solid Snake would be dead in seconds if he ever f'd with us!!

And GoldenEye on Wii :P

uh... I think for all spy games its a standard lol

Had another but forgot it, maybe it'll come back in a few, all nighters tend to do that to a man 

Damn!  Snap!

Nice thread.  Couple of points:

1 - surely the undisputed king of man sized vents is Half Life series?  Not only are they everywhere but they feature in set pieces aplenty and even get their own self referential in-joke in Episode 1 (it was EP1 right?)  Few games have vents all over the place and the confidence to joke about it

2 - Deus Ex 10 out of 10. Corrent and great taste.  Invisible War 9 out of 10?  Wait what?  Don't be so generous, knock it down to 8 where it should be

3 - Sly Racoon surely features Racoon sized vents rather than man sized vents

I could be wrong but I thought there were vents in the Subspace Emissary in SSBB.

Chrono Trigger, Grandia, and FF7 had them.  That's how we break out of jail!