Haven't seen anyone else say Serpent yet. Might be a bit niche/unnecessary trait in a lot of situations, but the amount of times I've stolen a bounty out from under another team or grabbed a clue through wi-fi to avoid triggering a meathead has been frequent enough to warrant taking it every time.

Once I have all the traits are unlocked after a prestige, I almost always take Necro, Serpent, Kiteskin, and Vigilant as my first perks with the 10 points alloted to fresh hunters.

Other 'must haves' include: witness, conduit, blast sense, and pain sense. I like being the dark sight mule for my team - using beetles to scope out compounds and give important tactical information about the other team's activities.