Middle Back Rows
Improves posture and is important for rotator cuff health and function.
If you're doing this properly, you don't need much weight. The body cheats by bringing in momentum (by moving too fast) and also by having your elbows drop slightly down, which brings in your lats rather than the rear shoulder, rear cuff, and scapular (shoulder blade) stabilizer.
Keep your elbows high (at shoulder level throughout the entire movement) and lean backward with your elbow tips, imagining strings attached to your elbows, pulling them backward. You should feel the muscles working behind your shoulders and around your shoulder blades. (Another version of this exercise can be done with elastic tubing and a tubing door attachment.)