Just so we are clear, I am referring to this game as the Dos version, not the unofficial remake or the App remake. I'm sure someone has played it this way, but it's too much of a child hood memory not to add it.
Probably one of the few games I played over and over, sunk hours into, as a kid growing up. Loved it, and I totally abused the selling glitch it had to get all of the weapons on level one.