Celebi can check Bulky Waters for Gyarados but Jolteon outspeeds Celebi and there is a chance it has Signal Beam so I don't know if Celebi can check Jolteon for Gyarados.
Return is also another option. The combination of Normal + Water coverage is only resisted by 2 fully evolved pokemon, namely Empoleon and Ferrothorn. Being walled by Ferrothorn is however a major disadvantage, and Return doesn't boast great power against bulkier opponents.
You forgot Jellicant.