The opening gunship shooting section is straight from Predator. The scene even includes complete with an extremely muscular, badass handshake and Little Richard's rendition of Long Tall Sally playing in the background.
The sound effect for changing vision modes also sounds very similar to the SFX from the series.
Sloan's facial mutations from Blood Dragon blood prompts Rex to call him "one ugly motherfucker".
When Rex selects the Terror 4000 minigun he "chambers" a round by twisting the barrels similar to how Blaine does when he lets 'Ol Painless out of the bag.
When he uses the Killstar to burst through the entrance to Sloan's base he quips "Knock, knock" before the bloodshed begins.
The A.J.M. note Double points for Alex James Murphy pistol is modeled on Robocop's "Auto 9" custom Beretta 93R, and even makes a direct reference to it in it's descriptionnote It's also the only weapon with an information text that is continuously reverent. All others are loaded with gags. Rex also twirls it around cowboy-style before holstering it like said character.
The Kobracon comes from Robocop's Cobra Assault Cannon.
The fact that Rex can't attack Sloan due to his programming is also a call to Robocop's Directive 4.
After completing any of the hostage rescue missions, shooting the freed scientist will cause "PROTECT THE INNOCENT" to flash in Rex's HUD.
Dr. Darling's look is strongly based off Ludmilla Drago.
The obligatory training montage invokes the training scene from Rocky IV. Specifically Drago's training with high tech equipment. Darling overseeing this whilst looking like Ludmilla only further cements the Shout-Out.
Sloan's chainmail clothing is almost identical to Bennett's from Commando.
Also similiar to Commando is the scene after the opening helicopter battle where Rex loads up on equipment similarly to Col. Matrix upon reaching the Big Bad's island.
One mission has you destroying nests of eggs with a flamethrower, followed by a battle with the mother while waiting for the elevator to arrive, mirroring scenes from the end of Aliens. Rex will even mention it "looks familiar" at one point.
Martial arts rock band Dragon Sound provide their hit song Friends for the ending credits.
The Killstar artifact you get near the end of the game is very similar to the Glaive from Krull.
Rex's line about being "85% synthetic" calls to mind a line from the obscure late 80s-early 90s cyberpunk movie Nemesis, in which the main character, Alex Raine, notes the line similarly, although he was noting that he was mostly human.
Rex's clothes are reminiscent to the outfit Snake Plissken (action hero played by Kurt Russel) used in Escape from New York.
Also, from Star Wars, there is the villain stating "I programmed you. I made you! I am your father!" and the response "NOOOOO!"