+1 on the S&W Sigma for this use. Cheap, very reliable, best customer support in the industry and its trigger means you won't be shooting anyone unless you really mean it, and won't cry too hard if its gets stolen with your car.
The current $50 rebate and two free mag deal really sweetens the deal , or if you are looking to get an AR, buy as S&W AR and get the Sigma for $99! These offers run through Jan 31, 2008.
--wally.