3v3 for 5 minutes like it currently is but add an over and back rule. The rule: If the puck crosses the blueline from the attacking zone into the neutral zone and was last touched by the attacking team, then the attacking team may not be the next team to touch the puck or else an icing is called against the attacking team. The resulting face-off will be in the attacking team's zone and the attacking team cannot change players.
The purpose of the rule change is to prevent teams from carrying or dumping the puck back out of the attacking zone just to maintain possession. Once you enter the attacking zone, you're more or less committed until the opposing team gets possession or clears the puck. This should hopefully lead to more chances in OT.