Right: He left his waitress a niggardly tip.
Perhaps due to the unfortunate similarity to another word, some people mistakenly assume niggardly is a racial slur of some sort. In fact, it simply means miserly or stingy. Still, due to the potential for confusion, perhaps it’s best to use a synonym instead.
This reminds me of the story of a politician who used dirty tricks in a campaign, by claiming of his opponent that “He has been seen masticating in public and his wife is a known thespian.” The politician evidently counted on the voters possessing poor vocabularies. Similarly, you might enjoy this spoof of a campaign speech by Bill Garvin, published in Mad Magazine in 1970: http://www.mendosa.com/politics.html.
Spaded vs. spayed
Wrong: Have your dogs spaded or neutered.
Right: Have your dogs spayed or neutered.
To spay means to have a female surgically sterilized. Spaded means shoveled as with with a spade. Do you really want to encourage people to shovel their dogs?
More next time.