An example of one-line joke that plays on words is that people can't explain puns to kleptomaniacs because they take things literally. Another play on words is that the dyslexic devil worshipper sold his soul to Santa.
Sometimes funny one-line jokes come from celebrities. For example comedian Rich Hall observes that hotel minibars allow people to see into the future by discovering what beverages will cost in 10 years. Pundit Stephen Colbert points out that internships give people the experience of a summer job without the hassle of a paycheck. Comedian Matthew Wohlfarth offers his own play on words by saying he works out "religiously" or on the religious holidays of Christmas and Easter.
Some one-line jokes are about death. For instance, a midget fortune teller who kills his customers is a small medium at large. Another joke is that people can kill vegetarian vampires with a "steak" to the heart.
One-line jokes often talk about money. One example is that people are born free and taxed to death. Another joke is that banks are places that lend people money as long as they can prove they don't need it.
Also there's the observation that the kind of shoes ninjas must wear are sneakers.