Stand or Fall

At the beginning of combat on your turn, for each defending player, separate all creatures that player controls into two piles and that player chooses one. Only creatures in the chosen piles can block this turn.

Grand Melee

All creatures attack each combat if able.
All creatures block each combat if able.

Fight or Flight

At the beginning of combat on each opponent's turn, separate all creatures that player controls into two piles. Only creatures in the pile of their choice can attack this turn.

Pramikon, Sky Rampart

Flying, defender
As Pramikon, Sky Rampart enters, choose left or right.
Each player may attack only the nearest opponent in the chosen direction and planeswalkers controlled by that opponent.

Raging River

Whenever one or more creatures you control attack, each defending player divides all creatures without flying they control into a "left" pile and a "right" pile. Then, for each attacking creature you control, choose "left" or "right." That creature can't be blocked this combat except by creatures with flying and creatures in a pile with the chosen label.

Space Beleren

Space sculptor (Space Beleren divides the battlefield into alpha, beta, and gamma sectors. If a creature isn't assigned to a sector, its controller assigns it to one. Opponents assign first.)
+1: Creatures in each sector can be blocked this turn only by creatures in the same sector.
−1: Put a +1/+1 counter on each creature in the sector of your choice.
−5: Destroy all creatures in the sector of your choice.

Chaosphere

Creatures with flying can block only creatures with flying.
Creatures without flying have reach. (They can block creatures with flying.)