Dragged vs. drug
Dragged is the traditional form and is still considered standard, but drug is common in some parts of the U.S.
Dwarfs vs. dwarves
Dwarves in fantasy fiction; dwarfs everywhere else.
Doppelgänger
= (1) a spirit double or counterpart of a person, or (2) a lookalike.
Douse vs. dowse
Douse = (1) to plunge into liquid, (2) to drench, or (3) to extinguish (especially flames). Dowse = to search underground using a divining rod.
Dam vs. Damn – What’s the Difference?
Dam: a structure used to hold back water, plus related verb senses. Damn: (1) to condemn, (2) to bring about the failure of, (3) to prove guilty, or (4) to send to everlasting punishment.
D’oh
= an interjection expressing annoyance, sheepishness, pain, regret, agitation, or a range of other emotions.
Dead set, dead-set, deadset
= (1) fixed on a purpose or (2) resolutely. It is usually two unhyphenated words.
Deceptively
Deceptively is often confusing because it can bear contradictory meanings, so it is best avoided when its meaning isn’t absolutely clear.
In This Day in Age or Day and Age – Usage & Meaning
Day in age is an eggcorn from the redundant phrase day and age.