What is your favorite [...Effect] or [...Bias]
in Social or Cognitive Psychology?

My #1 fav. may be:

[Fundamental attribution error], also known as correspondence
bias or attribution effect, is a cognitive attribution bias where
observers underemphasize situational and environmental factors for the
behavior of an actor while overemphasizing dispositional or personality
factors. (Wikipedia)

_______________What is a [.... Effect] term related to the following?

Confirmation bias: This is the tendency to seek out or interpret
information in a way that confirms one's existing beliefs, even if the
evidence is weak or incomplete. In this case, people with confirmation
bias might focus on the few data points that support their theory and
ignore or downplay anything that contradicts it.

Availability heuristic: This describes the mental shortcut
where people favor information that is readily available in their memory
when making judgments. This can lead to forming theories based on easily
recalled examples, even if they aren't representative of the wider picture.

Anchoring bias: This is the tendency to rely too heavily on
the first piece of information encountered when making decisions. People
with an anchoring bias might use the initial data points they encounter
as the foundation for their theory, neglecting to consider alternative
possibilities.