IMHO the best bike racks are the hitch mounts that hold the bike by the wheels and also clamp onto the bike frame, like this one:


or this one:

 

Trunk mounts scratch and dent your trunk. Some are not very secure at all, especially when carrying more than one bike.

Roof mounts make loading a heavy bike difficult and they tend to scratch up your roof. One must be very careful of LOW CLEARANCE areas when driving with a roof mount...(don't ask how I know...)

Hitch mounts that carry a bike by the frame are not too bad. They allow the bikes to swing but that can be minimized with some bungee cords. Carrying a women's bike that lacks a proper top-tube requires an adapter...

 

i can recomend this product as i have one myself, it is a detachable tow bar. when detached there are no signs of it being there. it is very useful and will only allow a cycle carrier to be attached to it, THEY ARE NOT MADE FOR TOWING !

Honda Civic Hybrid Cycle Carrier Towbar