Just got my Droid the other day and have been looking around for cool apps... just extraneous free things really...
(Pretty sure ALL were free...)

Here are some gun ones:
Mil-dot Calc: Just what it says - a Mil-dot calculator
Shooter: Havent worked with this yet - looks cool
SchottGunn: A shotgun.. that's it
AK-47: An AK to mess with
Gun Tones: A bit goofy - but hey - fun for a minute or two...
Ruger SR-9: that is all it is...

Some other good ones:
Radar Now: Current weather radar.
The Weather Channel: of course.
Akido: A book reader app.
Beer Cloud: Look up brewers, beers or scan the barcode for info on a beer!! This is cool.
Google Sky Map: Maps the constellations and stars overhead.
Nasa Wallpaper: yep.
Gstrings: instrument tuner
GPS Status: yep. with headings and accelerometer
Guitar chords1: Just chords.
Robotic Guitarist Free: Can play chords or independent strings. Coolest one yet for guitar - free.
White noise Lite: White noise generator w/ nature sounds.

Goofy stuff:
Labrynth Lite: (Wooden type - table top) Maze game.
Surveyor: looks cool - but haven't really messed wit hit...
Tricorder: Yes, tricorder.

Other cool stuff:
Warplanes: Warplanes backgrounds
United States Constitution: yeppers.
US Presidents: Just a study guide like app.

What have you found?
What do you think is cool?