I don't know if it's true or not, but I've heard that one of the best antennas can be a mylar balloon; tie a wire to the balloon and the other end to the antenna port of your radio and, supposedly, you get great reception. If anyone knows anything about, please let us all know.
The Larsen NMO 2-70 is a popular dual band mobile antenna, available from most ham radio dealers. I personally use a Larsen NMO 2-70SH, which is a shorter (18") version, because it's mounted on the roof of my pickup truck, just to keep the height down a bit. Works fine for me.
My vote goes for the NMO 270 B or NMO 270C the "B" indicating everything is Black the "C" indicating chrome both in the whip and coil. Very dependable and good SWR in the 450 band.