the M-577 APC (not to be confused with the Real Military Vehicle  of the same designation) was designed by Ron Cobb for Aliens.

The Vehicle was built on a Aircraft tug and is not capable of carrying passengers - (the interior was a seperate set)

Other than the mockup, there is no real vehicle of this design in production.

the Pulse Rifle (M-41A) is a Thompson SMG with a Remington Shotgun mounted underneath then encased in a custom shell with mock electronics. There is no real weapon in production.
Designed by James Cameron.

the M56 Smart Gun was built upon a MG42 Machine Gun and mounted on a Steady Cam mount. There is no real weapon in production.

Most of the Weapons and all the vehicles were designed by Ron Cobb, Syyd Mead and James Cameron  for the movie.

(All information sourced from : Colonial Marines Handbook, Aliens Roleplayin Game, Wikipedia, Science Fiction Modeler (Series of Articles 'how to design a spaceship'))