The Zeus Class Fusion Pistol is one of two energy weapons found in the game. It fires bolts of plasma which do a great deal of damage, but fly very slowly through the air, thus losing accuracy over distance. Secondary fire is a larger, more powerful blast that takes time to charge and costs more battery power. If the pistol is charged too long it will discharge and explode, injuring or even killing the player. It can be fired in a vacuum, but firing underwater will cause injury to the player.
Additionally, the fusion pistol is the only weapon capable of penetrating the super shield biobus enhancement.
"The Tech.50 is an extremely expensive weapon to produce and is used primarily by elite commando tactical troops. Normal firing mode produces 20 high impact energy bolts (5.83 TeraWatts each) in eight seconds. The secondary trigger will charge the internal MicroFuse Reaction Core to 17.5 TeraWatts of power; which is discharged in one large energy bolt. The Tech.50 is powered by a Deuterioxide Halogen Battery Pack capable of producing 116.6 TeraWatts of power."
- from Marathon manual
"The S'pht have done their best to create an infinite supply of fusion batteries out of the finite number you were transported on board with. If it were not for their ingenuity and industrious nature you wouldn't be able to run around firing with reckless abandon at everything that moves as you are wont to do. But, like the hundredth copy of a third generation duplication of a substandard bootleg -- they're a little fuzzy. One might even say unstable."
- from Marathon 2 manual
Have you tried your new fusion gun against the armored Pfhor hunters yet? My S'pht rebuilt it with the sole purpose of short-circuiting Pfhor-built machinery.
- Durandal, from Marathon 2, We're Everywhere, Terminal 1