Blade traps can deal quite a bit of constant damage if you can set them up and if monsters stay in their zone of effect.
I consider turrets to be traps, so if you can gather and set them up you’re set.
Mines are easy to scavenge and will end the lives of most normal-sized things pretty quickly. You can make them down the line.
Gun traps, this includes crossbows and shotguns and the like, are great but need to be reset once they go off.
Portal traps, created with portal generators that you can find in labs, are awesome underground because it’s almost guaranteed for things to teleport into a solid/impassible tile and instantly die. Don’t think about scavenging them though, it’ll take you ages to find the point they teleported to through mining and I’m not even sure the items will be there if you do happen to mine through the tile they teleported into. Portals are also good above ground if you’re lucky enough that most of the things that walk into the portals simply explode, which is an effect they have they have a chance to apply.
Ledge traps, basically just a z-level fall, can damage and kill a lot of things. Damage scales with amount of z-levels fallen I think. Examples of this trap without setup is two buildings who are close-enough together for the player to jump from one to the other. Most enemies cannot jump from my experience, so just about all enemies will simply fall off the building. Can be built if you are willing to spend the time on it.
A boobytrap is a trap involving a grenade and some tripwire. Pin is pulled on wire trip, grenade sets as active, explodes soon-after.
If you find lava that would be your go-to as a last-ditch to lead a horde to.
Pits, as you’ve said, are mostly for defense, but you can set up some just outside a town and lead its hordes to said pits. You can also upgrade pit damage with glass or spikes. I’ve also found that a fire pit, a pit with something burning inside it, is enourmously deadly.
Caltrops and nail-boards I consider to be the slightly more offensive traps in terms of being carried around and frequently deployed, but they don’t do much damage. Good thing too, because they’re actually pretty cheap to make.
You can carry around a bunch of braziers and flammable materials with a bunch of lighters and set up fire traps, but they’re likely to be smashed or destroyed. If you plan to use fire traps you can just carry around a bunch of rags and set them up to be lit as a wall of fire.
I consider glass bottles with acid to be one-use traps. Throw the bottle to a spot and it will splatter and fill a spot with acid. Most things are damaged by walking through acid or being directly thrown with the acid bottle. Same thing goes for molotovs, but they belong more in the fire traps category.