Just for fun - here is my list of 10 items - feel free to expand on the list.

(1) Sticky backed plastic covering that shatters like glass.
(2) U/C that spring back and allows the wheels to puncture the above sticky back plastic.
(3) Nasty horrible wood that is heavy and splits easily.
(4) Nasty plastic spinners.
(5) Nasty and un-airworthy control horns and quick-links.
(6) Overweight airframes.
(7) Lack of glue.
(8) Cheap plastic fuel tanks that split.
(9) Bits that rattle inside wings when you shake them.
(10) Appalling and unsafe flying qualities.