The cable crossover is a good exercise for targeting your inner chest.
It does require that you have 2 cable machines facing each other, but this is a common setup in most gyms.
Steps
Attach handles to the higher pulleys of both cable machines. Stand between the two machines with your legs and waist slightly bent. Grip the handles of the pulleys with your palms facing down and your arms out to your sides.
Slowly pull the handles down towards the floor until they touch or cross over in front of you. Hold this position for a few moments then return to the starting position.
Tips
When your arms are in front of you, contract your pectorals for a moment to make this exercise even more effective.