There's also a glitch you can do with the tiny Bond cheat on. If you crouch and walk slowly off a cliff, like a building at the end of the Dam, you will be able to float. Also, the glitch can be done at the top of the staircase in the bunker. That's probably what your friend was talking about.
I'm just going off memory, though. I was super into this game. I was into it before I found out about speed gaming. I never tried for speed, but I used to do strange things like beating levels with only the pistol, or choppers, and getting 100% accuracy without taking a hit. Stuff like that. The speed runs on the net (www.the-elite.net) are pretty cool, I think, because they save time by doing stuff I wouldn't have thought of. But sometimes the video is mostly just them staring at the ground, since apparently you run faster that way. Because of that, I decided not to do any speed attempts.