Here's a list of resources for you if you're looking for some help or inspiration. There's plenty of other options too, so use whatever works best for you and your idea.
- Pixel Prospector's Giant Indie Guide of Indie Resources
- The Game Jam Survival Guide by McFunkypants
- Puzzlem00n's Insightful Ludum Dare 23 Experience
- Global Game Jam 2012 Resources by scoreoid
- GameMaker (There is also a seperate Windows and Mac version)
- Stencyl - Great for 2D Flash games, requires no coding (just logic)
- Unity - Create 3D games with ease
- Inform 7 - Make awesome text-base games
- Flixel
- FlashPunk
- Axel
- Alpaca Engine - Open source point-and-click adventure game engine
- FlashDevelop - Windows Only, Free Flash IDE
- Notepad++ - Windows Only
- TextWrangler - Mac Only
- Sublime 2 - Cross-Platform, Free Trial
Adding audio to your game helps tremendously, so do it!
- Bfxr - Make great sound effects