It was probably me Tag.
Yes, GM has a credit card that you can get. It is just a MasterCard. But, being a GM MasterCard, you can earn "points" which when redeemed at the dealership, convert 1-for-1 into dollars that just come right off the top of the price. (I don't remember the conversion for "how much you spend vs how many points you earn").
However, they have some restrictions when redeeming those points. When I bought my '99 Silverado, I could only use a maximum of like 1800 points to redeem. Our '03 Tahoe we could only use 2000 points. And for my '06 Silverado, I could only use 1500 points. But, there are certain vehicles for which you aren't allowed to use points from your GM Card towards the purchase. I'm pretty sure you couldn't use any points on the Vette, the XLR, and the Solstice (this was like a year ago, so it may not be the same now), and I won't be surprised if you can't redeem points on the Camaro when it comes out.
Go to
www.gmcard.com to apply for a card and to read about it.