These are sometimes referred to as Eliminator Football pools as well. Entrants pick one team each week of the NFL regular season with the intention of the selection winning. If the team selected wins or ties, the entry survives to the following week. If the team selected loses, the entry is eliminated from the pool. If all remaining teams lose during a week, they all move on to the next week. The final surviving entry is the winner, unless there are multiple teams alive after Week 17. Teams may only be selected one time for the duration of the pool.
Losers - Pick Losers instead of Winners to 'Survive'.
Default Picks - Choose from several options to assign a team to an entry that doesn't make a pick prior to the deadline.
Strikes/Lives - Allow teams more than one 'loss' or 'strike' prior to them being eliminated.
Start Week - Want to start a 2nd chance survivor pool? Start a pool with the first pick some time after Week 1.