Stamina implant

The Stamina Implant allows the player to increase his Stamina Stat by 10. You are required to give the voucher to Gerard to receive the upgrade. You are given one by Macil each time you complete a mission.

This item is considered much more beneficial than the Accuracy Upgrade because the Stamina Stat affects both the player's health cap, and in addition, increases the strength and damage of the Punch Dagger.

A side note is that in Strife-supported versions of ZDoom, the player can give themselves the Stamina Implant with the GIVE console cheat. Although the player's punch is unaffected by the stat, their natural health cap still goes up whenever given one, and this works in Doom, Heretic and Hexen games in ZDoom in addition to Strife itself.

An additional note is that in ZDoom, spawning a Stamina Implant voucher with "summon upgradestamina", and running over it will automatically add 10 to your stamina/health cap, unless the player is already at the maximum for their stamina stat. Again, this works in Doom, Heretic and Hexen games in addition to Strife itself.