I use a Dymo Rhino Pro 5000 and it is great for a variety of things we do at work. Possibly a cheaper version of the Dymo label maker might be the go for standard work.
...2nd the Metallic Sharpie, best on dark surfaces though..also possibly even more durable are oil-based weatherproof "paint pens"-- I get mine from Abbeon Cal; but you have to order 15 for $44. I can tell you from experience these things last for ever until you use them up -- I have had a few sitting around for over 5 years and they're still good!
http://66.70.117.13/store/item.cfm?code=2107 Mark Permanently with
Real Paint Pens on plastic, glass, leather , stone,
wood, metal, paper, etc.
An opaque, weatherproof, non-toxic enamel . . .
dries to a glossy finish in seconds . . .
smooth application with the pressure sensitive felt tip . . .
pen-size for convenient handling
shake for 60 seconds to insure proper mix of paint . . .
writeout 150 meters.
Size is 53/8" long x 5/8" diameter.
Any mix of colors per package.
I use the little Brother P-Touch. It works well as longa s you clean the surface before applying it. I like the various colors, including clear backgrounds and various metalic colors. The gold lettering on black looks really good on a black flashlight.
In a few cases, I've used a drop of super glue to make the hard to stick label permanent.