Not a unique find, but it made my week.
A couple of ELWs, a terraformable and a pair of moons with 7 biologicals on each. Kept me busy for a few days.
Minable deposits in the ice rings would have been a bonus, but you can't have everything.
I don't know which is rarer, two ELW's in the same system, or two Water Giants in the same system, but I would surmise the latter is pretty up there...