I'm thinking about the kind of traps players may find when exploring ancient ruins. I have some pretty pointed views on the subject which I thought I'd share.
If you are thinking of dastardly modern traps I'd get a copy of Grim Tooth's traps to get your (Creative? Bloody?) juices flowing. Usually you don't need anything too complicated for most players;

First, you must understand the purpose of a trap. Is it a safety system gone wild? (Halon systems will kill you.) Is it to kill? Who is it to kill? How lethal is it? (If its there to stop a grave robber, it should be utterly lethal for a average grave robber. i.e. a one way ticket to the bacta tank if the player survives.) You shouldn't penalize the players trying to resolve it but always remember how lethal it needs to be. (A Jedi Decapitator would obviously be pretty lethal to average EOTE players. But maybe not so much for Jedi who are trained to duck.)
In game terms the Emperor (that's want I call myself) needs to determine what the mechanical purpose of the trap is. Is it to consume player resources? Is it to challenge the players by removing one from their midst? Is it part of a combat challenge? Is it for levity? How will it affect the story arc and narration? "Snakes. Asps. Very Dangerous. You go first."
How old is it, and how has it aged? Folks, entropy is b*tch. Batteries age and wear out, metal rusts, chemicals react, semiconductors degrade. If you want ancient ruins full of functional stuff, I recommend some sort of stasis field that stops time. (Always unstop time when the players least expect it. What fun!) Traps that stand the test of time need to be low tech, and use very long life materials. 'Treasure' in the form of equipment would probably difficult to adapt and use. "Does that Sith vibro-sword take D cells? No? Too bad."
Really ancient ruins may have other issues. Like global warming, ice age, exploding asteroids, etc. In that case the terrain and climate my be utterly alien to when it was built. If you came across an empty diving pool complete with diving board on the moon, it would certainly give you a pause for thought. What if you found that in the arctic? "THIS IS CETI ALPHA FIVE! Ceti Alpha VI exploded 6 months after we were left here. The shock shifted the orbit of the planet, and everything was laid waste!"
But back to traps. Passive traps are the easiest to set up, are very effective, and long lasting. In the real world if you want butterflies in your gardens, you could A) buy some, B) buy butterfly food, C) plant butterfly food to obtain a never ending supply of butterflies. This provides an interesting challenge for players. "Look... Cozy Worm droppings in the jungle... Did anyone bother to check whether that was the primary food staple for Krayt Dragons? No!"
The food chain is your friend. No one sleeps under the Rancor Tree, at least not more than once.

Mechanical traps are ideally not very complex. Shock devices should be relatively easy, drop a magnet through a giant copper coil, and you got giant lightening bolts of pain. (Actually this happened to a friend, someone dropped a screw driver in a sonar coil.) Falling rocks, and rolling boulders should be easy enough to implement. Remember folks, its the little things in life that bring pleasure. Try not to make it complex or do lots of things, they should also be single use. One shot, one kill should do the trick.
I've done all these things to my players in fantasy games. Naturally, they are a very nervous lot.
Assassin vines in the apple orchard. What a fun day that was. ![]()
Rotting bodies create methane... flint golem... steel swords... *Boom* Wizard was blown clean out of the room, and knocked out. Fighters were dazed and confused dealing with the aftermath. ![]()
Monk falls down pit and takes a lot of damage. As he's struggling to climb up, some guards come along and offer him a rope. Just as he's clearing the edge, they let go of the rope. *Womp* Monk stops moving. ![]()
Darkness... don't forget to turn out the lights every now and again. Works best if the guy who can see says something like, "Duck now." ![]()
Ah... and who could forget the log suspended a long ways back from the door. The rogue wouldn't touch the door knob, so the fighter said, "I'll do it..." *boom* he was sent flying backwards right into a sticky mushroom patch followed by a swarm of zombie hands.
(In Star Wars, fire ants would be fun.... Yeah real fire. You wanna do it. You know you do.)
So long, and remember... don't walk into the stasis field.