Rambo's weapons have become almost as iconic as the character himself. The "Rambo" knife has become so widely known that almost any large survival or bowie knife is often referred to as a Rambo knife. In the movies, Rambo's other weapon of choice is his bow, sometimes used with exploding arrows.
Rambo's bow really became popular after the movie "Rambo II" was released in 1985. Stallone had a custom built Hoyt Spectra bow with glass limbs and Omega wheels, which transfer the cables laterally during the power stroke, obviating the need for a cable guard.
Hoyt/Easton later released a commercially available bow package based on the Spectra model (which included the Streamlight flashlight stabilizer, a custom "survival knife" with compass and necessities kit, take down arrows made by Easton, and a few other odds and ends including a rather well-thought out backpack for the whole thing) used laminated limbs and normal wheels, with a cable guard.
For Rambo III Stallone used a Hoyt ProVantage with a 90 lb. pull. It is all I can do to draw this one back. I was told that they wanted a hard pull to accentuate Stallone's flexing muscles.
In the new movie "Rambo" , Stallone reportedly used a Hoyt Matrix and a Hoyt Gamemaster in the film. He requested the Gamemaster at 70# and traded for 50# limbs after a few weeks. This apparently has to do with the fact that he's expected to remain at full draw for unreasonable lengths of time during the filming process.
I have read that the "exploding tips" were actually the "Razorbak 5" broadheads in their protective plastic covers and painted gold.