As far as I know, this hasn't been posted yet.
non-combat companions aren't supposed to trigger traps, the fat dwarven chick that follows you around if you've obtained the Archaeology piece "The Innkeeper's Daughter" can trigger traps, best case scenario you'll get the daughter to eat a hunter's freezing trap.
I discovered this by accident when I was doing EotS and she was following me around, she got frozen, I targeted the trap and lo and behold the fat lass had gotten herself trapped.
If she appears in arenas, this is double nice.
*edit - additional info*
I just confirmed this and it does work (not tested in arena yet) but for all of you hunters out there, the innkeeper's daughter can also be killed, so make sure you kill her before she eats one of your traps.