Amagon by Sammy, for NES - released in the US in 1989, I think I like the JPN title better "Suddenly! Machoman!" because, well, that's usually what I hear whenever I enter a room!
Amagon is another in a series of countless me-too platformers that reared it's head on the NES/Famicom in the late 80s, justrun to the right, jump over pits, and don't get killed by monsters, bats, and jumping fungi. Yeah, the usual. You had a rifle, giving it a little of a Contra notion, though your ammo was extremely limited - if you ran out, then you'd be batting enemies with the stock of your gun, making for much more difficult gameplay.
The real gimmick here was that your little soldier could pick up a "Mega Key," empowering him to shed his shirt and grow into a large beefcake warrior known affectionately as "Megagon," jumping through trees and killing stuff much more gracefully and easily. Yeah, sort of the Super Mario effect I guess. Of course, get hit and you're back to wimpy mode again.
This game never caught on - it didn't ever look too interesting, and there was not much to it, and also it was difficult! Something about the way the control handled - it wasn't bad, but it was rough! Still, the game always stayed inthe back of my head for some reason or other. It's world was colorful, rich and perky, and I appreciated what the dev's were going for. This game was definitely a test, and unlike so many other titles at the time, it did not feel like just another sloppy piece of shovelware.
An interesting note is the final boss, who looks ripped off (directly!) from a Space Harrier boss. I never noticed anyone else ever mentioning this - I'll do a side-by-side in a Space Harrier someday. This stuff happened once in awhile, but it always made on scratch their heads.
If you are up for a challenge and eager to prove your worth as a true Machoman, you might wanna check out Amagon!