A good strategy for using PhD Flopper to its best effect on Ascension is to just buy it early on and then keep diving to prone near where the perk machine is found. By doing this it is possible to get to round 20 with minimal use of ammunition. However, as this is an explosive "weapon", it should be noted that the player only receives 50 points from each kill, when opposed to the 70 points that are acquired by using a bullet firing weapon, so using a gun would be advised if the player is going to buy something, such as other perks. This perk though doesn't seem to work when diving right on top of multiple zombies. It should also be noted that is generally advisable to dive to prone away from any teammates, as landing on one will down both players.
Ascension - Near the Northern Lunar Lander, near the wall with the purchasable grenade
Call of the Dead - In the abandoned second story/floor of the multi-story building that branches off of the lighthouse
- The name is a play on words on Dr. Pepper and PhD (Doctorate of Philosophy)
- PhD Flopper is made of prunes, according to some of Tank Dempsey. This is a reference to the myth that Dr. Pepper contains prune juice
- When you overcook a grenade, you do not get hurt
- The bottom of the machine says Flopper PHB