You can use curl bars for a variety of bench presses. You can use a curl bar for close-grip or neutral-grip floor bench presses or use them on a variable angle bench to perform incline or decline bench presses as well.
Also, you can use a curl bar to perform pullovers by laying on a bench with the bar over your chest and slowly lowering the bar as far over your head as possible with slightly bent elbows, then returning the bar to the original position.