The Mercenaries - Gain boatloads of time...easily!
There are two areas in the city in The Mercenaries where there are hordes of zombies shuffling around near a red barrel. If you can shoot the red barrel when they're all close enough, you'll gain well over a minute (maybe even two) added to your time. From then on, you should have enough time to run past most of the remaining enemies and make it to the warehouse, although you can use the time to rescue the hostages at a slightly more relaxed pace.
Here are the locations:
Y-Shaped passage. This is the passage next to City Hall. At the Y-shaped point, there's a red barrel. There are 10+ zombies in this area, and you can usually kill all but one or two in the blast when you shoot the barrel.
Courtyard outside of the Raccoon Press Office. Most of the zombies (8+) are in range of the red barrel, so when you shoot it, the blast should take out the entire group, save for one or two wandering outside the entrance to the Press Office (which you should enter, if you want to save a hostage. See my other Hint for more details on the hostages).
This is extremely useful to remember when playing The Mercenaries, especially if you're playing as Nicholai.
Added by: Volke Dec 14th 2009, ID#899