In Act 5, after defeating Screaming Mantis, Snake will come across two long rooms filled with Scarab robots.

If you have the inclination, time, and ammunition, you can have Snake destroy these tiny enemies for 100 Drebin Points each (they spawn infinitely until Snake touches the exit to the next room).

Just remember you can run out of ammunition, and the difficulty level will affect how much damage each Scarab takes. Don't spend more ammo than you can earn back.