Ninja Spirit
Ninja Spirit is a hidden treasure, released on multiple platforms, but this version is just fantastic. It features 2 levels of difficulty: PC-Engine Mode, and Arcade Mode. The main game is the same, but in Arcade Mode, anything that can do damage, KILLS YOU INSTANTLY. PC-Engine Mode has a life bar, but there are still a ton of things to kill you.
There are 7 levels in the game, mostly going left to right, but a couple move vertical. When you reach the end, you fight a boss. It's a short game, but VERY difficult to defeat (luckily, you get unlimited continues).
I've made hundreds of attempts, but right now have 2 successful versions (I consider it successful when I have 0 deaths).