Main page: Dead Rising.
Raining Zombies (20 )
How to unlock: Knock at least 30 zombies over with a parousal.
Grab the umbrella of a picnic table and hold X to activate its charging attack. Use that attack to kill zombies. Once thirty have been killed, this achievement will appear. A parousal can be found as soon as you leave the safe house for the first time either in Fortune Plaza or Leisure Park on top of picnic tables.