Warning: This comic occasionally contains strong language (which may be unsuitable for children), unusual humor (which may be unsuitable for adults), and advanced mathematics (which may be unsuitable for liberal-arts majors).
A random, non-exhaustive list of xkcd’s that were highly effective in making me think ( and laugh! :P)
Ayn Random is pretty much objective.
The Monty Hall is not a difficult problem at all.
What if headlines were written to garner more clicks?
What do you want to do with life?
The sweetest illogical logic in life - Love.
You know this if you have ever contributed to the wikipedia.
String thoery and science.
Sounds more like an Armageddon.
A Green Flash?
T.I. will always be hated.
Definitely the sweetest among the whole of xkcd.