Overdrive is a shooter made by Jordan Browne using Game Maker, which can be quite difficult to play partly due to it's restrictive controls. Your ship can only move in four directions, and a key press is required for each shot.

But the game does has it's own charms, for example the introduction of boss battles every five stages or so and multiple enemy types which are different in each level. The unlockable menu can be activated by holding the left shift key and pressing Z at any time, although it is quite beatable without any cheats whatsoever.

Name: Overdrive
Developer: Jordan Browne
Category: Shooter
Type: Freeware
Size: 2MB