Standard Shell (1 Shell, 0 Rage, Normal Speed) - Your typical shotgun blast.
Solid Slug (1 Shell, 0 Rage, Normal Speed) - ???
Solid Shell (1 Shell, 3 Rage, Normal Speed) - ???
Crowd Control (1 Shell, 0 Rage, Delayed Speed) - Hits everything in the damage cone, but not quite at full power.
Just so it's clear, you do not have any way to kill all of the imps without getting attacked.