21 Flags

21 Flags is a recurring reward/immunity challenge that debuted in Survivor: Egypt.

Tribal
Appearing twice as a tribal challenge, each tribe takes turn taking 1,2, or 3 flags from a collection of 21. Using strategy and teamwork, the goal is to be the tribe taking last 1-3 flags that are available. Whichever tribe(s) take the final flags will win immunity, being safe from Tribal Council.

(Note: When performed with 3 tribes, the two tribes to not collect the last flags will face off in a 2nd round, and the winner of that round will also win immunity.)

Individual
The castaways face-off in a bracket-style competition, with a contestant being eliminated in each round. This will continue until only 2 castaways remain, where they will compete one final time, and the winner of that round will be granted immunity.