Popper
Makes the single strongest case against your plan before you commit.
Runs one disconfirming pass on a plan before you commit: the assumption that would kill it, the strongest steelmanned counter-argument, the blind spot someone smarter would catch, and the cheapest 24-hour test to disconfirm it.
Founder the day before a launch: the load-bearing assumption, the strongest case against, and the dry-message test you can send before launch day to learn if the wedge is real.
CEO about to send a senior offer: what you are missing because the candidate pattern-matches your last good hire, and a 24-hour reference probe with a clear fail signal.
Operator about to make a six-figure bet on a channel or partner: the assumption that would make the spend worthless, and the cheapest probe before the wire goes out.