Pacer

Pacers are headless monsters with a bloody neck. They can be spawned when a Gaper, a Flaming Gaper or a Frowning Gaper is killed. They behave by simply wandering around the room aimlessly making them only a real threat when escaping another enemy or in areas with less movement space.

Gusher
Gushers wander around a room blindly, similar to Pacers, but will occasionally shoot a blood shot in whichever direction they happen to be moving in. The shot is slow-moving and has short range, and is typically easy to avoid. Gushers are only a threat in large numbers and enclosed areas. Gushers are sometimes difficult to distinguish from Pacers due to their blood splash effect blending with the background.

Splasher
Splashers wander around a room and randomly shoot shots. They can be spawned when a Gurgle is killed. Oddly enough, Splashers that are spawned from Champion Gurgles appear as Champions but Splashers that spawn naturally in layouts are never seen in champion form, even if using the "CHAM P1ON" special seed.

Black Globin's Body
Black Globin's Bodies walk around aimlessly, occasionally spawning a spider. They can be spawned when a Black Globin is killed, along with a Black Globin's Head. Though they appear to resemble headless Nulls, they are unrelated.

Level 2 Gusher
Level 2 Gushers are an enemy added in The Binding of Isaac: Repentance. They run around a room blindly, occasionally spitting up Small Maggots.