>>48203062Ingame guides from Smogon's community ranks Lapras as B tier and Cloyster (Shellder) as D tier.
https://www.smogon.com/forums/threads/pokemon-heartgold-and-soulsilver-in-game-tier-list-mkii.3665471/Updated in 2020. Lapras has perfect coverage in Thunderbolt and Ice Beam, an immunity with Water Absorb, and some utility with Sing/Confuse Ray. It doesn't need dual screens from other teammates to patch up defenses either. You can use Lapras to it's full potential without breeding.