Clawed lobsters typically have two differently-sized pincers. The larger of the two is the crusher, and it's used for -- you guessed it -- crushing through the shells and carapaces of its prey. The smaller of the two claws, the cutter or seizer, grabs onto meat and shreds it into smaller pieces so that the smallest antennae can carry it into the lobster's mouth.
Lobsters tend to have a dominant claw -- meaning that they are either right-clawed or left-clawed -- and their crusher claw can be on either side. Juvenile lobsters start out with two cutters, and one develops into a crusher over time as the lobster locates objects to pick up. Scientists have been able to induce lobsters to avoid developing a crusher claw, but not to generate two crushers -- those have only been seen in the wild [source: Cowan].
No matter which claw is dominant, the lobster isn't all that attached to it -- literally. If a lobster loses a claw or leg, it will grow another when molting. Molting happens several times a year until the lobster is a full-sized adult. During molting the carapace splits and every hard piece is shed. Any missing limbs regrow during this time, and are identical to the original. A lobster can also drop a limb or claw if necessary to save its life, such as to get away from a predator. This adaptive phenomenon is called autotomy or reflex amputation [sources: McCarthy, NOAA Fisheries Service].