I mean, somewhere where you think, man, you guys should go somewhere else to fight, the surroundings around you or events around you are likely to kill you both!!!!
One such place I can think of is where Anakin and Obi-wan are fighting on Mustafar and everything is falling apart around them and lava is everywhere and it seems very likely both are gonna get killed.
Personally, I had such a scenario in my LBT finale fight where Littlefoot and the Terror of the Mysterious Beyond are fighting in the Mountains that Burn (you know, that crazy place full of tar, lava, bones, and very wicked Domeheads) during a second Great Earthshake.