Psycho

Psycho appears to be a form of injected drug composed of strange, unknown chemicals of military origin, that comes with its own unique delivery system. One canister contains a mixture of speed and heroin. It was designed at the orders of General Constantine Chase and is supposed to increase the combat potential of a soldier, whilst dampening higher mental functions, making for fearless, but uncontrollable troops.

Fallout, Fallout 2 and Fallout Tactics
Psycho has another beneficial effect not intended by the programmers. When taken, it reduces Intelligence by 3. This can be exploited to boost your skill points. First, raise a skill to the point it needs two skill points to be increased, then level up. When you level up, take two to reduce your Intelligence greatly. This will correspondingly lower your skills involving Intelligence (Science, Repair, Outdoorsman, Doctor, etc). Now allocate your skill points to the skill you want raised - since the skill's value has been lowered, it will take only one skill point to do so. Then rest for a few hours. When the Psycho wears off, Intelligence will be restored, and the skill will be given a significant boost. This is particularly useful for getting a 121% Science skill to recruit Skynet without taking Mentats or wasting too many skill points.

Fallout 3
Psycho is very common in the Capital Wasteland. It is sometimes sold secretly, requiring dialogue and possibly a speech check to convince the proprietor. There are around 60 in set locations in every game.

Locations

 * At least one dose can be found in Silver's house
 * Several doses can be found in the Super Duper Mart
 * Frequently found in Raider establishments
 * Sold by Doc Hoff, Cindy Cantelli, Ahzrukhal, Leo Stahl, and various other vendors.
 * Three can be stolen from A Quick Fix in Rivet City.
 * Four can be stolen from Cantelli's Room in Rivet City.
 * dead bodies of Wastelanders.
 * Can be found on the corpses of Talon Company Merc.
 * Sold by Wasteland Junkie around burning barrels in the wastelands, along with Jet Mentats and other addictive chems. (Random Encounter)

Bugs
Sometimes the damage counter in the pip-boy 3000 will partially be affected by the 25% damage bonus, making weapons look more effective than they are in reality. With the other damage modifying perks, Ghoul Ecology and Superior Defender from Point Lookout, unlucky players can get the Xuanlong Assault Rifle standard 64 damage titled so much that it can show up to 180 damage on the pip boy. (Confirmed on 360)

Appearances
Psycho appears in Fallout, Fallout 2, Fallout 3, Fallout Tactics and the cancelled Fallout: Brotherhood of Steel 2.