Since so many people have yet to reach first prestige or 54-55 (for claymores) you see bouncing betty's everywhere. People think these will actually protect them. But their wrong ! muahaha
If you see a bouncing betty guarding a room, simply dolphin dive or go prone and crawl right up to the bouncing betty. It will fly in the air, then explode, doing no damage to you at all. Thats your oportunity to wait for the opponent to see whos coming and you kill them.