kick·er 
(kĭkər)
(kĭkər)n.
1. One that kicks: stayed clear of the donkey known to be a kicker; the team's kicker who kicks field goals.
2. Informal
a. A sudden, surprising turn of events or ending; a twist.
b. A tricky or concealed condition; a pitfall: "The kicker is that the relationship of guide and seeker gets all mixed up with a confusing male-female attachment" (Gail Sheehy).
3. A condition that imposes an automatic increase, as in a pension plan.
4. A small outboard motor.