A cognitive bias is a systematic pattern of deviation from norm or rationality in judgment. Individuals create their own "subjective reality" from their perception of the input. An individual's construction of reality, not the objective input, may dictate their behavior in the world. Thus, cognitive biases may sometimes lead to perceptual distortion, inaccurate judgment, illogical interpretation, or what is broadly called irrationality.
For obvious reasons, it is much easier to identify biases in others than ourselves. Nevertheless, some of us went through practices (such as psychotherapy), experiences, and introspection that allowed us to put our biases in check. So, instead of scrutinizing the behavior of others (something that comes naturally to us, especially on the internet), here I ask you to exercise some self-criticism. What intellectual tendencies you have that obsessively repeat themselves in different contexts?
I should note that cognitive biases do not always lead to bad outcomes or falsehoods, as stated in Wikipedia:
Although it may seem like such misperceptions would be aberrations, biases can help humans find commonalities and shortcuts to assist in the navigation of common situations in life.
On this thread, I am deliberately not asking about political bias or anything of the sort, including all the juicy controversial subjects surrounding it. Anything that often leads to uncivil discussion should be considered out of bounds.
For inspiration, look at this list (you don't need to identify a named bias, though... a subjective description of something you believe to be a form of bias is enough).
Dear Mods, due to the contentious nature of the subject, please feel free to act more aggressively on this topic than you currently do.