So some brief context: Terminal Velocity doesn't have a limit on how fast any of the weapons should fire as long as the game registers that you pressed the fire key, if you can send such a event nearly every frame the game processes at, every weapon will spray like a firehose. (Practically like Privateer 2: The Darkening now that I think of it)

Though, I'm curious to find other games that act this way. Is it possible to write and run a TSR of some sort that's able to do what I'm able to do with a desktop macro, or dosbox's joystick autofire? If so, can these work even in protected mode or am I stuck with real mode only games?

All I need is some way to autofire any arbitrary keycode in MS-DOS.