In Mercenaries mode you can reload your weapon by pulling up your Inventory screen and combining the ammunition manually with the gun (using the "Move" command button). Once you get used to this, you can use it to your advantage since it is a lot faster then reloading your shotgun, for instance, on the fly. More importantly, you can use this trick while climbing a ladder or when you are a jumping down to really save some time -- and possibly your neck.

Hint: Unlimited Money and Ammo

Unlike in Resident Evil 4, your ammo and money carry over every time you replay a level. Collect money and ammo in a chapter; then pause, save and quit. Restart the chapter and you can collect everything a second time. This works well in chapters 1-2, 3-1 (the hovercraft level) and 4-1 (caves). As a general rule, this "farming" method works especially well in levels in which you can collect weapons worth money and ample hidden treasures like jewels and beetles. For instance, 3-1 has copious amounts of treasures, and a Rocket Launcher on the sunken boat that you can repeatedly collect.

Unlockable: Versus Characters

Below is a list of the unlockable characters for Versus Mode (downloadable content) and their costs in the game's exchange points.

* Safari Chris - 8,000 points
* S.T.A.R.S. Chris - 13,000 points
* Clubbin' Sheva - 6,000 points
* Tribal Sheva - 15,000 points
* BSAA Jill - 5,000 points
* Battle Suit Jill - 7,000 points
* Midnight Wesker - 30,000 points
* S.T.A.R.S. Wesker - 50,000 points

Some Tips I found on the net