Dragon Temple

Two green monsters and two purple switches.

The two switches need to be activated at the same time.  You’re not going to be able to do that yourself, so you’ll have to get the monsters to do it for you.  Your shots won’t kill these monsters, but they do freeze them for a moment.  Shoot at one of the monsters when it’s standing on a switch, and wait for the other monster to stand on the other switch.

And that unlocks the exit?  Not quite.  But two more switches have appeared on the wall, and if you shoot both of those (while dodging the monsters) the door will open.