As a developer, there will be times that you will need to pitch a game to a group of producers, investors, peers, etc. Over the past few days I've watched quite a few pitches from my peers for various games without a variety of results. Frankly there are many things that you should be thinking about in this situation to help make your pitch a success. A presentation of some kind helps, games are a visual medium so your presentation should be visual as well. Yet you could get by without one, though I would certainly say it's not recommended. You could have a working prototype of your game that you put together from pre-existing material so people could potentially play the game to get an idea before hand. Once again though, it's extremely helpful but not always an entirely possible route to take. There is though one thing that I would say is absolutely indispensable when you are pitching a new game: excitement.