Ball Revamped IV: Amplitude
John has returned to the original stationary playing field from his previous scrolling version in both parts of III, and added plenty of new obstacles and power-ups in 100 new levels to keep you satisfied for a good half an hour or so. Controls are the usual arrow keys, and [P] for pause.
Although some of the obstacles are recycled from past versions of the game, there is plenty of new material to keep you satisfied. The level design is great, and as always, every ten levels introduces a new stage. This means the music and background change, and new power-ups are often added, too. My only complaint would be the looping music clips are incredibly short and get annoying quickly. Even more annoyingly, there does not seem to be a mute button, so you'll need to mute the main volume control of your computer. However, this is more than made up for by the great physics and amazing level design. Overall, an excellent addition to a great series of games.
Cheers to Shang and DooMerPS for suggesting this one. =)
Update: Sound can in fact be turned off from the pause menu. Thanks, Role!