Fisto! can be found in the upper area of the derelict power plant right across from MDPL-13 power station, next to a terminal on a desk. This is northwest of Minefield. Inside the power plant are multiple feral ghouls, and, depending on your level, you may also encounter multiple feral ghoul roamers, glowing ones and, with Broken Steel installed, feral ghoul reavers. It will be in poor condition (approx. 20%) when found.
Used in V.A.T.S., a critical strike results in a brutal uppercut, often sending the enemy (or quite often just the head) into the air.
Of all the Unarmed weapons, Fisto! has the highest base damage, the highest DPS (damage per second), and the highest damage per Action Point value when using V.A.T.S. However, it is little over a third the damage per AP of The Terrible Shotgun, and has a lower MDPS (that factors in critical hits) than the deathclaw gauntlet.
Targets that are below the Lone Wanderer's knees, when the player attacks them with an Unarmed weapon in V.A.T.S., are kicked rather than punched.
Behind the scenes
First revealed in IGN's week of Fallout 3 coverage, the Fisto! had been described as multiple shards of metal wrapped around the player's fist but was revealed to look just like the power fist.