This one bugs me almost as much as the pilot who makes the straight in at an uncontrolled airport....

When pilots read back their callsign first, and then the request.

Controller: "United XXX runway one zero clear for takeoff"

Pilot: "United XXX clear for takeoff runway one zero"

Sounds like two requests from ATC and if you have two aircraft with similar callsigns, then your just asking for trouble.
This is like radio communication 101.