This section started by Andreas Koch.

- Atari XG-1 Light Gun (shipped with Bug Hunt cartridge for the XL/XE.  Also
  shipped as part of the XE Video Game System box package);
  http://www.mr-atari.com/afbeeldingen/hardwarediv/xesystemgun2.jpg
- Atari G1 Light Gun (same as XG-1 but shipped with Bug Hunt cartridge for
  the 7800/2600)
  http://gamingmuseum.classicgaming.gamespy.com/g1lightgun.jpg
- "The Best" Light Gun by Best Electronics (a sort of self-made (?)
  Light Gun);
* Sega Light Phaser for the Sega Master System (normally not Atari compatible;
  but can be converted into an Atari compatible light gun easily);
- other light guns (most of these have to be converted)...

Note: After having 3-4 Atari and at least one (converted) Sega light gun,
it is my personal impression, that the Atari light gun merely works ok 
on/with TV-sets (and not at all with a monitor), whereas the Sega light gun
works alright on TV's and (most) monitors. Since I never had a Best
light gun I cannot comment on this one... (Andreas Koch);