Naturally, these are the things that will change your stats and give you a chance at kicking ass. The starting weapons are small, but as the game goes on you'll find bigger and nastier things to play with. Items will also have limits on their bonuses, as indicated by parentheses ( ).
Let's say you pick up an item that has the following:
Offense +1 (6)
Defense +1 (6)
Speed -1 (4)
If your Offense is already a 6, you will not get a +1. Likewise, if your Speed is a 3, it will not take a -1. Now that that's cleared up, let's see the three types of items you can have.
Firearms
Guns! Hooray for guns! Firearms have a lot of punch and a lot of noise. Firearms give a little boost to Offense, but they're especially good for upping your Ability. On the downside, Firearms are also loud and hurt your Stealth by a small amount. Some of them are also insanely heavy and/or powerful and may drop your Speed and Strength by very low amounts. It's up to you though: Do you want to run around with a 9mm handgun, or do you want to stand still and fire off a mini-gun? If the situation arises where you have to choose between two Firearms, pick which one you think will help your more.
Melee Weapons
These are the nasty bastards you use when you're up close and personal. They don't afford you the range of a Firearm, but when push comes to shove your Melee Weapon may be what saves you. Melee weapons generally favor your Offense and Defense while giving your Ability a small boost as well, but since they require more than a simple trigger squeeze, even the smallest knife will net you a Speed penalty.
Extra Items
These are random objects that aren't necessarily full-on Firearms or Melee weapons. These will give a minimal boost to one stat and come with no penalties.
Joke Items
Some Firearms and Melee weapons are completely useless crap. They do not boost any of your stats and in some cases offer you nothing but penalties. Getting rid of them is very much advised.
Healing Items
New to the BR game are Healing items, which can recover some of your HP. The smaller ones are freebies that will be dropped randomly, but the big ones will require a difficulty level to be beaten by the dreaded d10 die. Ooooh, scary! Or not.