System Shock Infinite is the unofficial sequel to System Shock 2.
The custom wrench deals extra damage to energy targets.
The custom assault rifle fires in very rapid bursts, with a smaller clip and bigger knockback.
The custom positron rifle is fully automatic, but less ammo efficient and with a smaller clip.
The custom fusion cannon has a larger clip and higher rate of fire, but is less ammo efficient.
The Wrench is from Opposing Force, nice.
The pulse rifle is from AvP2 - nicer!