The term 'enemy shooter' can refer to any of three (Or four) sprites. As used on this page the term 'enemy shooter' refers to an invisible sprite that regularly produces visible, dangerous sprites. In three cases this is used to give the illusion of a tile-based gun regularly shooting bullets into the level. These are Patch:Enemy shooter (Keen 3), Patch:Enemy shooter (Keen 5) and Patch:Enemy shooter (Keen 6).
It is also possible to include the Patch:Dart Gun in this group, though it is given a slightly different appearance. and more complex mechanics. The Patch:Watermelon in Keen Dreams may also be included though they are visible sprites (but similar to the dart gun in mechanics.)
Due to their production of new sprites, misuse of these sprites can cause the game to fill up with sprites and crash.