ummm everyone forgot about the beast that is Lapras its easily my favorite tank its strong has a decent sp.A and Sp.D and with leftovers , Toxic,Rest,Sleeptalk, hydropump/icebeam/surf
or you can go for the stall and go with A lapras with Hydration with a damp rock spam rain dance then rest when you need to , then set up with dragon dance and the waterfall everything xD