Set health/damage values of player weapons/enemies
During single-player mode, type sk_ at the console window and repeatedly press TAB to cycle through the values. The sk_plr_ values are for the player's weapons, while other values are for enemies and health/shield chargers. The 1, 2, and 3 at the end of the syntax corresponds to the difficulty settings easy, normal, and hard. Set their values accordingly. Enter a number, a space after the syntax, then type restart to confirm the changes. For example, sk_plr_rpg1 99999 makes the rocket launcher in easy mode inflict 99999 damage with a blast radius that wipes out the entire level.