I've seen it said on several Chesterton sites, that Chesterton is the most quoted author of the 20th Century. I guess you'd have to expect that on a site devoted to Chesterton. Freely copying from the American Chesterton Society's web site then, here are a few quotes for your review:
Timeless Truths
"Misers get up early in the morning; and burglars, I am informed, get up the night before."
- Tremendous Trifles
"Fallacies do not cease to be fallacies because they become fashions."
- ILN, 4/19/30
"I agree with the realistic Irishman who said he preferred to prophesy after the event."
- ILN, 10/7/16
"The Christian ideal has not been tried and found wanting; it has been found difficult and left untried."
-Chapter 5, What's Wrong With The World, 1910
"These are the days when the Christian is expected to praise every creed except his own."
-ILN 8-23-28
"There are some desires that are not desirable."
- Orthodoxy
"I say that a man must be certain of his morality for the simple reason that he has to suffer for it."
- ILN 8/4/06
"Art, like morality, consists of drawing the line somewhere."
- ILN, 5/5/28
"The aim of good prose words is to mean what they say. The aim of good poetical words is to mean what they do not say."
- Daily News.4-22-05
"Atheism is indeed the most daring of all dogmas . . . for it is the assertion of a universal negative."
-"Charles II" Twelve Types
"If there were no God, there would be no atheists."
Where All Roads Lead