To make your level skyrocket to level 50 go out to Fortune Park and head towards the Atlantica Casino. Don't go in. Instead, follow the wall right until you see a maintenance door. There should be a stick of dynamite and a hunk of meat right outside the door. Pick both of these up head inside and combine them, to get the dynameat. Leave and head right to the fireworks stand. Grab some firecrackers and jump up on top of the stand. Lure a large amount of zombies near you using the firecrackers, then when you feel your group is large enough, jump into the middle of the crowd and use the dynameat, and get out quickly. The resulting explosion will cause your PP bar to go through the roof with points. All of the items respawn when you leave Fortune Park and come back so you can do this as many times as you like. This trick is still very effective at levels 45+.