doesn't need to be in context (i.e no need to use roman numeral designations, simple pop/jazz/rock/contemporary chord symbol will do, but you can also use the academic name, i.e. tristan chord, mystic chord, german 6th, etc).
we'll keep it fun and light hearted so i won't harp on anyone that doesn't actually state a favorite but lists a few (which seems most people do, i seldom see a question like this asking for a singular favorite and people actually staying w just one, but rather a list....i digress).
bonus points if you state more than one as a progression, i.e. two chords in a cool progression, i.e. one resolving or leading to another cool one. dont worry about the voice leading, just one chord name to the next is enough.
just curious.