Minor rant aside, I'd like to see an old classic re-added, which is the T-virus gun. A traitor only equipment with one shot, where the player shot by it is given 1 minute before they die and turn into a hl2 zombie npc of any variant (except crawler zombie), who all have reasonably high health and strong damage for anyone trying to fight it up close. Usually, it took the form of a coloured silenced pistol that makes the targets screen flash green on hit, and has them slowly over the duration have difficulty aiming.