"Might come in handy!"
—Kyle after a bonus drop appears
Sometimes, killed zombies drop bonuses, which provide the player with extra health, ammo, money or blueprints. The health bonus and blueprint drop is unique to special zombies, and the others can be dropped by any other zombie. They also vary in rarity. Currently, there are four kinds of bonus drops present in Dead Trigger 2.
Money bonus is one of the most common bonuses the zombies can drop. It can be dropped from any zombie and each zombie seems to have the same chance of dropping this bonus. Special zombies always drop several money bonuses (usually 3-6) at once. The amount of money the player gets from this bonus varies per level of Tech the player has. (Seems to start at $20 and increases by 50% per tech level). At Tech level 9, the money bonus is worth up to $5000000 (after 0.5.0 Arena Update it is reduced to $458 with the Money Booster and 229 without it). The money bonus drop is a large bundle of money.
Another form of money bonuses are Goldehhhjjn Pigs.
Ammo bonus, along with money bonuses, are the most common forms bonus drops. As the name suggests, it provides the player with additional ammunition for their weapons. The chance of dropping this bonus seems to be the bigger the less ammo the player has. Special zombies often drop this bonus when they're injured, to balance the fact that they need a lot of ammo to deal with. The amount of ammo received from this bonus is applied to one weapon, but it's usually from half a magazine to an almost full magazine. The ammo the player receives for a certain weapon is dependent on the weapon used to kill the zombie. The ammo bonus drop looks like an ammo strip.
Health bonus is one of the rarer bonus drops, as it only drops from special zombies, and not all the time. It replenishes a bit of player's health, less than the Painkillers do. The amount of health replenished seems to be random, but it's approx. 20% of health capacity of the player. When picked up, a slow-motion effect also occurs, same as when using Painkillers. Its icon resembles the Red Cross.
Blueprints are the most valuable items that can drop. However, they are also the rarest, dropping only from Special zombies at random. The probability of getting a blueprint from killed special zombie is unknown, however it seems to slowly decrease as the player progresses trough the game. Blueprints are used to unlock new weapons and items and allow them to be built when the required Tech level is achieved, and when the player has enough money. Each weapon and item requires different amounts of blueprints (from two to eight).
See Blueprints for more detailed information.