Labyrinth was one of the first iPhone apps to offer a lite (see also: free) version of the game for people to play through before forking over the cash for the full version. This tactic convinced thousands of people to download and try this really neat puzzle game.
The game utilizes the accelerometer to allow you the ability to tilt and move your iPhone in an attempt to guide a metal ball baring to its end goal. Along the way there are pieces of the maze that stick out and block your path, pegs to keep you from sliding through a short cut, and plenty of holes that will bring you to the beginning of the maze.
If you have ever played with a real puzzle like this before, you'll enjoy the same addictive nature in a more compact fashion. The puzzle can be more complex without the actual size of the object in your hand having to be bigger due to the level developers simply redefining the size of everything to make it fit. Labyrinth responds very well to every slight tilt and turn, but you can't quite get the same effect out of nudging it that you can with the actual puzzle. This isn't a steep learning curve, but it will take some getting use to.
Once you beat a level, you move on and try another. There's 10 levels to try in the free version and plenty more in the full version, so if this type of game interests you, you won't find yourself bored very easily. Unfortunately due to how simple of a title this is, many people will stick with the free version and save their bucks for a game like Monkey Ball (which ironically utilizes many aspects of this older puzzle style). The lite version is a must download, but not necessarily something you'll be keeping on your iPhone for a long period of time.