The PSI blades (also called "swords") are high damage, energy-based melee weapons. Swords come default with the campaign and any map that does not specifically disable them. A player wields two, swords, one on each arm. These weapons appear to be attached to the arms, and then can be shut off, as it is possible to fire weapons and use equipment without the swords getting in the way. PSI Blades are capable of instantly killing low-health enemies. However, in later levels of the Campaign, four or more hits may be required to kill an enemy. The color of the swords depends on the character, like the blood. In multiplayer, these weapons are almost always fatal in one to two slices, due to the fact most maps have players with low health.
The damage they deal is arguably more potent than that of the Heavy Railgun and the CS-BNG. Multiplayer sword battles are often the most gruesome, with swords frequently removing limbs from enemies, leaving them to die slowly. When this occurs, the disabled player is considered free game, as the player must continue using a Defibrillator, if there is one, or they will die soon. When this happens, players will often scramble to kill the dying player. It is not uncommon in multiplayer for two people to mutually kill each other with their swords because they are so powerful.
- This is the only weapon in the game that can attack accordingly to someone's clicking speed, meaning that clicking at a fast rate will make your PSI blades also attack at the same rate, potentially doing more damage than any other guns if used right.
- If you slash with PSI blades at just the right moment, you can deflect bullets. This does not include explosives and energy projectiles, such as rockets and rails. It is recommended to use the Time Warp to do so, but this is only available in singleplayer and some "slowmotion" maps. It is also easier to deflect projectiles while underwater.
- A surprising effect about the PSI blades is that you can walk a little faster and jump a little higher while equipped with the PSI blades.
- In the Campaign, don't use your PSI blades to kill strong enemies without the Time Warp activated, as they will pull out their PSI blades and most likely kill you first. Enemies are generally more skilled with PSI blades than the player.
- If you switch to your swords you take1.5 more damage, meaning if an enemy aims you with a powerful weapon (eg CS-BNG), switching to a gun will be a better choice, as you won't take as much damage.
- In the games StarCraft, and its sequel StarCraft 2, a unit for the Protoss called a "Zealot" uses PSI Swords.
- Some nicknames of the PSI Blades are Plasma Swords, Glow Blades, or just "swords".
- Swords can be removed by an Engine Mark by typing "nopsi" in it, or by a trigger with activation type 49.
- When approached too closely, enemy AI will often switch to the Psi Blades and attack in close quarters, potentially causing the player to die soon if the enemy is not retreated from or destroyed.
- This happens on the maps that have deactivated the swords too, making the enemy harmless.
- Almost all of the swords are at the same size, other than the Heavy Battlesuit's, which are bigger. However, there are no advantages: all swords deal the same damage and have the same range, which mean small swords' true range and visuals don't match.
- Despite the swords originating from the hand, the Android SLC-56 has its swords inside its arms.
- When you are killed, your swords disappear.
- You can deflect grenades as well. You only need to slice the grenade many times and very fast. Such speed is unlikely to be possible without the Time Warp or any other kind of slowmotion. Using the Kinetic Module is an easier way to move grenades, however this is only for singleplayer.
- PSI Blades were first seen in Plazma Burst: Forward to the Past, used by Sword Bot on level 16. They looked a bit different than the blades in PB2, however.
- This could mean the technology used to make PSI Blades came from Sword Bot, which could also mean the Falkoks were the first ones to make PSI Blades.