Grimaced & Grimmest

Grimaced – (v.) past tense of Grimace, an expression of displeasure.
Grimmest – (adj.) the most grim.
So, yes, maybe I grimaced because I was the grimmest.

Breach & Breech

With an A – (v.) break through from one area into another.
With an E – (n.) hind section of an object or animal.

Berth & Birth

With an E – a sort of smallish sleeping space, or other designated area such as for docking boats.
With an I – a sort of smallish person undocking from its mother.

Scoot & Scute

-oot – (v.) a little bit sliding, a little bit shuffling, just kinda nudgin' along, y'know?
-ute – (n.) a bony plate such as the ones that cover a turtle's or armadillo's shell.
Speaking of which, whaddaya think of that cute little turtle? 'Scute, isn't it? :)

Frees, Freeze, Frieze

Frees – third person present verb form of Free.
Freeze – lose enough heat to turn from a liquid into a solid.
Frieze – a wide, architectural and/or decorative band that runs horizontally along a wall beneath the ceiling or roof.
If cold weather causes your paint to peel, then you might say a freeze frees the paint from your frieze. I mean, you MIGHT say that...

Taro & Tarot

Without a T at the end – tropical plant whose edible root has a surprisingly high nutritive value.
With a T at the end – prophetic playing card with no substantive value at all.

Ewes & Use

As in, "I can utilize the wool from those female sheep."

Deference & Difference

As in, "These aren't exactly homophones, but they're very similar and easily confused. So show a little respect and be sure you can tell them apart." :)

And, please remember, they are not to be confused with:

Forth & Fourth

As in, "After the first three butterflies emerged, the fourth came forth."

Straight & Strait

Which direction did the boat sail between two outcroppings of land?
Strait.
Ba-dum-bum.

Gnu, Knew, New

This one goes out to Yvonne Treis, who emailed me recently to suggest it (possibly because she knows I like doing the animal ones best). In other words, she asked for this new post because she knew I'd want to draw the gnu.

Links & Lynx

As in, "You really shouldn't chain up a wildcat."

Vain, Vane, Vein

Oh, man, I can't think of a sentence that uses all three of these in an interesting way. You?

Penance & Pennants

As in, "I feel guilty for even knowing that the World Series is on right now."

Rappel & Repel

With an A and two Ps – a method of descending a vertical surface.
With an E – push apart.

Him & Hymn

Tide & Tied

Lead & Led

With an A – a heavy metal, atomic number 82.
Without an A – past tense of, well, Lead. Oh, sheesh, that's confusing. "Lead/Lead" would be a good candidate for Homographs, Weakly, if I decided to branch out a bit.

And speaking of heavy metal:

Cornet & Coronet

Keep calm and scabba-dabba-doo-bop. I think Louis Armstrong said that.

Tighten & Titan

And for those who like their Titans a little more astronomical, and a lot more Proper Noun: