Best way to cut up a cheesecake into bites
My grandmother's favorite method for cutting cheesecake is dental floss.  Waxed or unwaxed shouldn't matter, though waxed may help keep cake from sticking too much.  Just be sure not to get a flavor!

Grip the ends tightly, the way you would if flossing your teeth and pull evenly down through the cake.  Then release one end and pull the floss through the cake.  Do NOT pull the floss back up.  Repeat as necessary until you have the size pieces you want.