Not myself (never really tried Cloyster anyway), but I see Life Orb and Focus Sash are common. Though if I used it myself I'd probably not use those items, because of the after mentioned reasonsI run White Herb on my Shell Smash Cloyster and nearly every Poke that tries to revenge kill it will not KO if they are a physical attacker. Then I KO their Poke on most occasions and sweep from there - it's a really fast, powerful setup.
Just curious - who runs something else on Shell Smash Cloyster and why? I can see a Life Orb, but with Sandstorm being rather common, and entry hazards there too, I have trouble sweeping with a Life Orb...