This is a variation of a close-grip pushup. Assume a Push Up position, however position your hands close together under your chest. Touch your two thumbs and pointer fingers together, making it look like a diamond. This exercise primarily works your triceps but also hits the chest really well.
Assume a normal push up position. Bring your feet closer to your body, similar to a handstand position but with your feet still on the ground. Lower down and up, again similar to a handstand push up.