There are a few more candidates for Serene Grace flinchers.
Cinccino @ Kings Rock
Ability: Skill Link
EVs: 252 Atk, 252 Speed, 4 HP
Nature: Jolly/ Adamant
-Bullet Seed
-Rock Blast
-Tail Slap
-U-Turn
Same as Skill Link Cloyster, Cinccino has 41% of flinching something with a 5 hit move. It has wider coverage as well, and more moves to make use of Skill Link.
Shaymin-Sky @ Leftovers/ Sharp Beak
Ability: Serene Grace
EVs: 252 Sp. Atk, 252 Speed, 4 HP
Nature: Timid
-Air Slash
-Seed Flare
-Substitute
-Leech Seed/ Earth Power/ Synthesis
You can't use Shaymin-Sky in wifi battles as of Gen V, but maybe Gen VI will change that mechanic.
Dunsparce @ Leftovers
Ability: Serene Grace
EVs: 252 HP, 252 Sp. Def, 4 Sp. Def
Nature: Careful
-Glare/ Body Slam
-Coil
-Headbutt/ Rock Slide
-Roost
Hey, it works; what can I say. Dunsparce is susceptible to status like Toxic & Burn though, since it's slower than all the others.