Mechanical hazards by themselves are, of course, somewhat limited in their ability to provide tangible threats to experienced PCs. The obvious solution is to combine them with living opponents at the same time.

Why have a combat scene take place in a boring corridor or room when you can have it take place on precarious catwalks over pits of boiling lava, while Edgar-Allan-Poe-esque pendulum blades swing amongst the fun? Heck, throw in some bats to obscure vision as well.

Hmmm, bats carry rabies, don't they? I hope your characters have good saving throws versus disease too.

Transcript

Anakin: So, it's... 1 and 4, 3, 2 and 6, pause, 1 and 5—
Padmé: No no no, wait, it's 1, 3 and 2, pause, 4 and—
Pete: Two flying creatures land next to Anakin.
[SFX]: Whooom! {Anakin swings his sword}
Padmé: Or... was 4 before the pause?
[SFX]: Whooom!
Anakin: I don't know, which bit are you talking—
Pete: Another one flies at you.
Padmé: Never mind. I'll just run through as fast as I can!
[SFX]: K-chunk!
Anakin: No! Stay where you are for a second!
Padmé: What if I wait for the first one, then run through to the gap between 2 and 3?
Pete: A creature fires a ball of green goop.
[SFX]: Ga-bloop!
[SFX]: Whooom!
Anakin: You'll get stuck under the welder!
Padmé: The welder's in sync with 3, I'll be able to—
[SFX]: K-chunk!
Anakin: That's it. I'm going back to look for another way around.
[SFX]: Ga-bloop!
[SFX]: K-chunk!
Pete: Look, this is not hard!