Ben Canning

Ben Canning is man found at seemingly random locations in the Capital Wasteland, sitting and begging for water. However, unlike the water-beggars found outside some towns, he only seems to take one bottle. After being given one, he proceeds to drink it repeatedly (was drinking Nuka-cola in my game ...); when activated, he apologetically tells the character that he's not up to traveling yet. Standing after a minute or two, he simply says "Good to see you again, friend!"

He can be mezzed, therefore, he can be enslaved.

Afterwards he can be found outside of settlements (in the spot where traders stand), loitering. Ben Canning has been seen near the Super Duper Mart being chased by raiders, he doesn't seem to register the fact that a bus in flames is a ticking time bomb

Locations
Ben Canning has been spotted at a number of locations, as noted by individual players below. Since he is a random-encounter event type, a more exhaustive list of locations where he may be found is detailed in the article Fallout 3 random encounters.

He has been spotted buried in sand, except for his head and one arm, near the minefield quest.

He has been spotted in the barn with a silo west of Vault 101. After drinking, he got up and headed west.

He has been spotted at the WKML Broadcast Station. After drinking, he headed south.

He has been spotted at the MDPL-05 Power Station.

He has been spotted at the MDPL-16 Power Station.

He has been spotted at Broadcast Tower KB5.

He has been spotted at the Meresti Trainyard.

He has been spotted at the old Temple of the Union.

He has been spotted at Paradise Falls.

He has been spotted at the extreme North-West sitting in the middle of the highway leading to Raven Rock.

He has been spotted near the Deathclaw Sanctuary.

He has been spotted sitting outside the entrance to Alexandria Arms.

He has been spotted near the Jalbert Brothers Waste Disposal.

He has been spotted, after giving him dirty or purified water, at the Canterbury Commons and Megaton traveling traders spots. (Still, all he says is: "Good to see you again, friend")

He has been spotted on the 1st floor of a demolished building on western edge of D.C. That building is located south-west from Sewer Waystation, west from Grayditch, south-south-east from Megaton, north from Red Racer Factory and north-west-west from Marigold Metro Station.

Notable Loot
If you find him dead, you will find:
 * Dirty Water
 * Head Wrap
 * Laser Pistol
 * Microfusion Cell (5)
 * Roving Trader Outfit