Standard floor presses are easy on the shoulders since the range of motion is reduced. That shortened ROM also places more emphasis on the triceps and helps you build lockout strength. Add a band to the mix and you can turn it into a great pec-isolation exercise.
Banded Single-Arm Floor Press
How to do it:
Loop a band around the bottom of a squat rack or something sturdy.
Lie on your back with the band stretched toward your body.
Grab the band and the dumbbell with one hand.
Press up toward the center of your chest until your arm is locked. Rotate your palm in so your shoulder is externally rotated.
Lower to the floor with control while rotating your palm forward.
Don't relax your arm at the bottom. Instead, keep constant tension and put about half of your arm weight on the floor at the bottom of the press.
Do 8-10 reps for 2-3 sets using each arm.
No band? Do the same move with a cable pulley handle (minus the dumbbell).