Here are the worst double standards that I have seen:
1) If a person of X ethnicity, where X is different from the norm in that country, commits a crime, suddenly that person's ethnicity is a focus point. If a person of Y ethnicity, where Y is the majority ethnic group in that country, commits a similar crime, suddenly no one pays attention to his or her race.
2) Gender X can do something and it's seen as no big deal, Gender Y cannot do the same thing. Both women and men do this. Men tend to severely look down on a woman having multiple sexual partners, but tolerate or, hell, even respect a man who has had many sexual partners. On the other hand, Women state that Men are shallow and pathetic for giving importance to physical attractiveness when considering a mate, yet women also have important appearance standards, and apparently that's "not" shallow: Case in point, if a man doesn't want to date a women because she is fat, that's apparently "wrong". If a woman doesn't want to date a man because he is shorter than her, then that's absolutely fine. In my opinion, BOTH genders have an absolute right not to date anyone they find physically unattractive! Men have a right not to date fat women, and women have a right not to date men shorter than them. Another case in point: If a man turns down or scorns the affections of a woman, the man thinks nothing of it. If a woman turns down or scorns a man, the man often gets very angry and throws a fit, as if he had a right to be liked by a girl (which of course, he does not have. No one has a right to be liked. NO ONE. A lot of men have a lot of trouble with this concept, sadly).
3) A poor or middle class person commits a crime. They are punished. A rich or famous person commits the same crime and often gets no punishment or a very minor punishment. This one annoys me the most. How many people have been given years and years in jail because they were caught with drugs or unregistered firearms, yet Lindsay Lohan and many other famous celebrities and rappers get only a few days in jail or a slap on the wrist?
4) Politician A changes his plan. Supporters of A say "what a wise politician! So pragmatic and willing to compromise!", while Supporters of B say "What a gutless flip-flopper. But if Politician B also makes a change or backs down from a plan, supporters of A will say "oh, he's a no-values coward!", while supporters of B will make up any excuse under the sun to justify the change.
5) America does something wrong, and it is rightfully condemned. But when France or Italy or Germany or Russia or China does something even worse, fewer folks pay attention.
Double-standards exist amongst every group. Every group, ethnicity, nation, gender or political party has self-interests and they always forbid their opponents to do what they do themselves. Double-standards come with being human. I have double-standards, YOU have double-standards, EVERYONE has double standards. This doesn't mean we should accept double-standards, but we need to be aware that everyone and every group has them, and that we live in a non-perfect world populated with non-perfect people.