Nail said:
Describe the Trapped Magic Items you've used.
A bit more general list is glyphs, cursed items, poison, dye, custom made magic items, spells, hired creatures, people of influence, and so forth.
Custom made magic items were pretty much that though, custom made. Most all were tuned to a certain character and anyone not that character would suffer in some way. Often with one of the above working in conjunction such as slipping a cursed ring onto someone, giving them some poison, making their skin turn a different color, alerting someone/something to the problem, and so on.
I liked the belt of many pouches modification where one of them was actually a bag of devouring. If someone who was not the wearer reached into one it was always the bag of devouring.
Glyphs are obviously easy and should not need any explination.
Although not a trap there is also the magical contract that binds those who sign on it in some way. This is an item that can be fairly expensive but sometimes necissary for the party to actually function. It also is worth nothing as loot. Something similar could be tied to a few items that function like little traps, if they deem that you were somehow responsible for another characters death that is wearing one it does something bad to you, like explode.
Sometimes it is even worth it to pay a bit extra and get an item enchanted so that it works for you and no one else. Especially if this is known to others. Having it be cursed for anyone but yourself is even more expensive but if you are knocked unconscious and people take your cloak of fun happy slaughter time only to find out that while they are wearing it they are drained of health while you gain it, perhaps even acting as a carpet of smothering it can make for a good time.
In a party with mixed races if you are the odd man out having the item work for your race while giving anyone else who holds it a negative level makes it pretty safe as well.
Items to keep from having to sleep as heavily or as long are common as well. Once the party of player characters has enough for everyone these lose their value as well.
Depending on the character in question just about anything is possible. Whatever makes sense and for people who are unlikely to trust one another some sort of precautions are very likely.