Pitfalls of high-falutin' language

The world is filled with writers of all kinds. Many are good, many are bad, many are mediocre. Usually it's not too hard to avoid low-quality writing; if it's awful, stop reading and go on your merry way, perhaps cleanse your palate with some worthier work.
What really becomes painful, however, is when otherwise good writers misuse words so blatantly that it sticks in your mind forever and festers there, like a tiny splinter from a seemingly varnished surface. There are a few misuses in particular that I see all too often, and that I wish to raise awareness about.

Don -- This is often used as a fancier-sounding synonym for  "wore." In actuality, it is a succinct verb that means "to put on." When used properly, it saves a bit of space and can improve sentence flow. Improperly used, however, it becomes a distraction and a nuisance.
Wrong: Anna was donned in cashmere.
Right: Anna had donned cashmere.

Orb -- It's not so much the misuse of this word as the abuse of it that is truly irritating. Since the English language doesn't have a lot of synonyms for "eyes," many authors will use the word "orbs" instead, either to avoid repetitive language or to sound more romantic. Either way, it never ends up sounding quite right, and those who enjoy it might find that its plebian cousin serves them better.
Wrong: Ambrose's blue orbs flashed with ire.
Right: Ambrose's blue eyes flashed with ire.

Thee -- Quite a few authors, when looking for a bit of medieval flair, have fallen at once to using "thee" without any thought to its proper use or conjugation. The most common mistake is to use "thee" universally, when in reality it is merely the objective case of "thou."
Wrong: If thee hast finished thee tea, I pray thee, come.
Right: If thou hast finished thy tea, I pray thee, come.

O -- This is a little bit nit-picky, I'll admit, but not a lot of people seem to realize that "o" is even a word. Most of the time, people just use "oh." "O" is used mainly in old-fashioned writing, often in legend-form, and is commonly a form of address.
Wrong: Oh mighty dragon, heed my plea!
Right: O mighty dragon, heed my plea!

Bonus: a Southerner collective noun explained
Y'all -- A lot of people get this one wrong, and it's used in different ways in different places, but believe it or not, there is a proper way to use this word! It's a contraction of "you all;" a collective noun that refers to more than one person.
Wrong: Y'all sit down, Mr. Parson.
Right: Y'all sit down, Mr. and Mrs. Parson.