1) The Prime Mover

The necessity of an intelligent prime mover requires a Being that is the ultimate cause of everything.  Such a Being would have to be the cause of all -- good, evil, death, suffering, tornados, tsunamis, earthquakes, sin, etc.  An intelligent prime mover is antithetical to original sin and atonement to God.  In fact, God would have to atone to us for creating such a lousy world that is the source of so much suffering.  A Prime Mover would be the intelligent Prime Cause of everything that occurs, which is, of course, certainly not at all what Christians teach.

2) "You can't prove a negative."

This is the classic argument that makes theists feel they are on safe ground that needs no defending because you just can't prove them wrong.  Nothing could be more self-defeating.  Regardless if the statement is even true, if a proposition is not falsifiable even in theory, then the proposition itself is rendered invalid and spurious.  You can't make a meaningful claim if it is beyond the possibility of reproach.  The statement only invalidates their own stand.  

3)  The watch on the beach

If the object found is discernable from its environment in such a way as to make it appear clearly intelligently designed, the environment is unwittingly being shown to not have been intelligently designed!  This is obviously completely self-defeating because the whole intent of the argument is to prove that things of nature are complex (like the watch), so they must have been intelligently designed.  Since we already know the watch was intelligent designed, the only thing the argument really proves is that the beach wasn't.  "The watch on the beach" is actually an excellent argument for atheists.