Finisher

[Raeanne Dimick]

One who finishes, puts an end to, completes, or perfects;
esp. used in the trades, as in hatting, weaving, etc., for the workman
who gives a finishing touch to the work, or any part of it, and brings
it to perfection.

[Couch Potatoe]

You know when youre jerking off and [cycling] through all those chick [in your mind]... well [the finisher] is the chick you finish jerking with.

[Michiko]

A person or thing that finishes something.