It's a rune as many have said/ You set em' off with an appropriate spell. Lightning for the purple lightning ones, fire for the fire ones etc.

Just cast Dispel on it. Oh, wait, that is one of the many many spell effects that was cut from the series. Too bad cause it would have been very useful here. Guess you just have to jump on it.

what's the action key trick? I can't "sling" anything without telekenisis, especially bodies

1. Wards
2. Almost any target spell
3. Throw a stick at it, or a body. Just grab something, look to the right, walk forward while swinging your mouse left and let go. The body will be flung a little forward.
4. Instruct Lydia to walk on it.

just like in normal combat, if a follower takes more damage than their current hp they die, forever

It's not easy. I do it by swinging around and releasing. Not to accurate with this either.

Action key is the key you use to Activate something.

This is why I spit a spell at the Runes now.

Become etherial

That's what followers are for. I often put the cursor on traps and told Erandur "Go there."
He never died, and never complained about it.

I stare intently at the rune, try to determine what kind of damage it deals, drink a resist potion for that kind of damage, then casually stroll onto the rune. Then I wait a while for my health to recover before exploring further.

Wow, am I the only one who uses the follower's option "I need you to do something" for stuff like this?

LOL! Up until now, that's mostly been my method of discovering them. "Oooh, what's that purty glint?" I'd make a lousy army minesweeper- they'd save big on my retirement benefits, though. Yeah, I think I'll just use those noob-level fire spells to pop them with, instead of trying to master some pick-up-and-spin-to-toss routine. Much simpler for an old geezer.

As everyone else said just a simple lightning rune just shoot something at it

That has to be the slowest and most inefficient method imagineable... but if you enjoy it, cheers!

People act like they're instant death traps...i play high elf with 150 health and weakness to magic and never had a rune kill me with full health

Yeah, I just make sure there are not too many enemies around and thet I am at full health when I set them off . . . Than cast a couple of Fast Healing spells and move on . . . But really wish there were a Dispel spell for mages to eliminate theset types of traps just cause it would be fun to dispel another mage's magic.

Cruelty is not for everyone!

I do not use the option beyond the point to tell a follower to sit down at home. Letting a follower pick things up or clear out a chest is still bugged. It can either cause items to get flagged as stolen when they should not be, or your follower's inventory fills up and you cannot clear it. There seems to be no weight check when you use this option (and gets used by some to cheat and to haul tons of stuff around). There are just too many bugs around followers and so I just leave mine at entrances and use them as simple mules.