It had to happen I suppose... Every games machine that respects itself, you see, simply has to have a game creation toolkit available for it and the iPad just got its very own. It's none other than the pretty impressive Codify. A powerful code editor with a ton of extras that will let you create almost everything you can come up with. Find it over at the App Store.
The editor costs a mere $7.99 and comes bundled with a ton of examples and tools, including a vector graphics renderer, sound effects generator, image renderer, syntax highlighter and more. This video should be most enlightening: