Doom's standard fist attack. This checks whether the player has the Berserk pack by looking for the presence of a PowerStrength item in the inventory. Damage is 2x 1d10, multiplied again by 10 when berserk. If the attack hits a damageable actor, the *fist player sound is played, on the weapon (CHAN_WEAPON) channel.
The range of the attack, which is 64, is determined by adding 20 to the calling actor's MeleeRange. Although the actor property could be used to alter the range, it is best to instead use the more flexible A_CustomPunch function to give an attack its own range. This feature exists only for MBF21 support.
You can implement A_Punch using A_CustomPunch. You can find an example of how to do this on that action's page (near the bottom).
This example is taken from Doom's Fist weapon.
Fire: PUNG B 4 PUNG C 4 A_Punch PUNG D 5 PUNG C 4 PUNG B 5 A_ReFire goto Ready