One of the finest puzzle platformers on the App Store, Mobigame’s Edge ($2.99), is currently free for a limited time. Edge was a standout release back in the early days of the App Store in late 2008, and then spent the better portion of the next two years battling a trademark dispute over its name.
Though the trademark dispute hogged many headlines during Edge’s lifespan, it was never lost on anybody that Edge itself was also a stellar game. If you somehow don’t already own Edge then you simply have to download it while it’s free to give it a try.
If you manage to complete all of the levels in the original Edge, a pseudo-sequel called Edge Extended ($2.99) was released last year which added and improved upon many aspects of the original.

Love this game. I'm playing Edge Extended on iPad 3 right now and it's glorious. It's so smooth and responsive.
I kinda wish they did more games with geometrical puzzles. How about one with a sphere? No tilt controls, though, it would have to keep the same directional controls as Edge.
Just downloaded it. I missed this one during the old 3G days. Reminds me of Marble Madness. I'll likely want to try the newer one as well on my iPad.