Game Maker

I was browsing around last night when I stumbled upon Game Maker v5.. It's a very cool game making program - it's versatile enough to do so many types of 2D, or pseudo 3D type of games (isometric, or fake 3D by scaling sprites).. You can do sidescrolling platform games (Sonic, Mario), Upward scrolling shooters (1942, Raiden), rpgs (Zelda).. it's definately capable of doing something like Space Harrier, Bomberman.. the list is endless - it really is up to your imagination.
It'll compile your game into one excecutable, and you can have the game running full screen or windowed if you like. You can build games that saves the highscore too. Sound effects can be imported, and the music format is Midi (unless you want a huge wav file to loop)..
You're allowed to sell what you make from Game Maker, if you wish, without any licensing issues.. The bad news is that, well, to get anything complex done, you'll have to ge your hands dirty and do some scripting.. Making your first game might be a bit daunting as you try to figure out how the whole process works, but it comes with some great tutorials.. so if you ever wanted to make your own game, and you've never gotten further than writing "hello world", then check it out [:)]

http://www.gamemaker.nl/

And check out some of the demos they have for you to download!
There are some naughty people who have ripped and duplicated some classic games, but they do show the potential of Game Maker.. They've done a Super Mario, Sonic, Zelda etc..