Types of Amunition
There are many types of ammuntion that you can find in the game.
The Rocket Launcher uses powerful (but dangerous) rockets, you will not find a whole lot of them around, and when you do, it will receive 1 rocket when it is just one laying around, and a box of rockets hold either 5 or 10 rockets.
 Energy Cells
The futurisic weapons, the Plasma Gun, the BFG 9000 and the Laser Cannon use this weird ammunition, it is very rare to find, but when you do, it quanity in them are worth the search, a small energy cell pack hols 20 charges and a large one holds 100 charges.