My slightly silly nomination is the Ranch Dressing Elemental.

The Order of the Stick having an alliance with an Elemental Prince (even if it's the Prince of Ranch Dressing) seems like it could be both funny and resourceful.

I also like to imagine Xykon being ambushed by these elementals and being covered in dip during the attack, which prompts the Monster in the Darkness to finally turn on and devour him since he smells so delicious.