Sternum chin-ups- This style of the chin-up was brought into popularity by Vince Gironda. These can be done with both a supinated ( palms facing you ) or pronated grip ( hands away ).You will focus on keeping the torso leaned back through the entire movement. You want the low portion of your chest to touch the bar. When you try to pull yourself up make sure to lean your head back away from the bar and to arch your spine throughout. Near the end part of the movement your hips and legs should be about 45 degree angle to the floor. Once you complete the movement your head should be parallel to the floor.
This is a great all around back developer. The beginning of the movement is like your regular chin-up, the mid-range is like the pullover and the end is similar to the row. I would not recommend this to the beginner but more for the advanced guy looking to change things up.
Subscapularis pull-up- Start with the normal wide grip pull-up position and bring yourself up until the upper pecs make contact with the bar. Once at the top try and push yourself away from the bar and then lower yourself slowly under control. Your subscapularis muscles are part of your rotator cuff and will help with you back strength and overall shoulder health.