The thread on easily confused words is a treasure trove of quirks of the English language; it also reminded me of this radio comedy game, which involves rather more radical confusions, as follows:
Capability: what good matadors have
Capable: what good matadors try to do
Inescapable; what Ines was told to do on her first day at matador school
Convertible: of butchers, to produce steaks
Digestible: to enjoy a steak
Incompetent: Bad at camping
Arrow: Where cockneys go to school
Fearsome: bad at maths.
Carbolic: humorous vehicle accessory, often found on trucks.
Diabolic: To make an ill-judged attempt at body art
Shambolic: On closer inspection, a gooseberry.
Any more?