Base & Bass

Base – the lowest surface of an object, upon which it rests. Similarly, a surface upon which another object rests, even metaphorically as a "base of operations." Also, chemically, the opposite of an acid.
Bass – the lowest/deepest range of musical notes, or the voice/instrument that produces them.

O, Oh, Owe

As in "Oh, don't worry honey. I owe the devil our first-born, but look how well I can play guitar!"

Pause & Paws

Q, Cue, Queue

Q are a race of all-powerful beings from an extradimensional plane of existence known as the Q Continuum – no, wait, that's not it. Q is just an O with a tail.
Cue – I'll just use the dictionary.com definition, because I don't think I can improve upon it: "a sensory signal used to identify experiences, facilitate memory, or organize responses." It's also the stick you hit balls with in pool/billiards.
Queue – fancy British word for a bunch of people or things lined up waiting for something.