RM - Suzuki Cappuccino
I can't reist a 1300lbs car with 125hp on soft racing tires. My ZR1 RM probably will take over this spot eventually, but I need to do a ton of tuning and modding (read: spead a butt load more credits on it) to get it where I want it.
As for LM, well I'm still working on that. Everytime I try to save up to buy one, I find 10 other awesome cars I want to buy and spend all my credits on them. Though, if the Minolta is anything like the Minolta in GT4, that will probably be my favorite LM car.