Once upon a time there was a game publisher called Apogee, and seemingly every month or so they'd release another fantastic shareware side-scrolling platformer game for DOS. One day the company unleashed Halloween Harry (later re-released as the renamed Alien Carnage), and I eagerly downloaded the adventure from a local BBS with my little 14.4Kbps modem using the mighty ZModem protocol, saving it to my meager hard drive alongside games such as Commander Keen and Boppin. Now, all these years later, Alien Carnage has been released as freeware by its creator so that today's gamers can roast aliens with flamethrowers and fly around with a jetpack. Hooray!
We later changed the game's name to the unfortunately generic Alien Carnage because sales for Halloween Harry were below expectations, and we feared that people thought this was a seasonal Halloween game. Looking back, probably the real killer was Doom, which clearly set a new standard for shareware games, a standard that took a few years for everyone else to catch up to. Still, this was a well polished, fun game that deserved a wider audience, and even today is worth a try.
If you don't have an old 486 MHz PC sitting around then you'll most likely need the DOSBox emulator to get this game running. It's worth the effort though, so don't be afraid to get your command line hands dirty.