One of the bullpens at my new job pitched in and got a pull-up stand! It brings people to visit and makes the place feel like we own it a little. That's a good selling point that it causes you to rotate your shoulder blades back and up. Hanging leg lifts can also be done and are also a much more effective ab exercise than situps (since it only takes 10 reps to get tired, and you can bring your knees closer or farther away to adjust the resistance).