I found a box of old flashbulb things once at a garage sale and bought it for $2. Thought it was junk. Turned out it was the exact "Graflex 3-Cell Flash Gun" type that is used in Star Wars as the light saber. Sold each of them for about $300 each for about $4500 profit. $2 -> $4500.
http://www.partsofsw.com/esbsksab.htm