Smogon official tier: RU
Base Stats: 60 HP, 70 Atk, 105 Def, 70 Sp.Atk, 120 Sp.Def, 75 Speed
“Usable” moves (according to Pokémon Showdown): Calm Mind, Charge Beam, Cosmic Power, Dazzling Gleam, Double-Edge, Drill Run, Earth Power, Earthquake, Extrasensory, Façade, Frustration, Grass Knot, Gravity, Gyro Ball, Hidden Power (Electric, Fighting, Fire, Grass, Ice), Ice Beam, Light Screen, Magic Coat, Protect, Psychic, Psyshock, Rain Dance, Rapid Spin, Reflect, Refresh, Rest, Return, Rock Polish, Rock Slide, Shadow Ball, Signal Beam, Sleep Talk, Solar Beam, Stealth Rock, Stone Edge, Substitute, Sunny Day, Toxic, Trick, Trick Room, Zen Headbutt
What distinguishes Claydol from other Pokémon in the RU tier is its unique typing and ability. Ground+Psychic with Levitate makes it one of the few Pokémon resistant to Ground+Rock coverage as well as Rock+Fighting coverage. Unfortunately, Pokémon who use those types generally have a way to get by walls like Claydol (either through their additional STAB or coverage moves). Fortunately, its bulk, although not the best, is respectable at the least; it’s mostly guaranteed to take any one hit. This helps with its variety of utility options: Stealth Rock, Rapid Spin, dual screens, and Trick Room. Actually, don’t use Trick Room on Claydol unless you absolutely need a Trick Room setter with such typing; it suffers in the same “valley of speed” (too fast for Trick Room, too slow for normal situations) as Malamar, only Claydol is actually faster. (Whereas min speed Malamar outspeeds anything uninvested below base 50, min speed Claydol outspeeds anything uninvested below base 52. This means even things like Registeel go before Claydol in Trick Room.) Another thing that sucks about Claydol is, while it has a neat offensive movepool, its offensive stats leave a lot to be desired. Heck, without its utility, Claydol would be pretty much outclassed by Cresselia—120/70/120/75/130/85 stats, enough offensive coverage in Psyshock and Moonblast to get by, and semi-reliable recovery in Moonlight.
Long story short, Claydol has interesting typing that lets it resist common types (Fighting, Rock, Psychic, immunity to Ground—thanks to Levitate—and Electric) but simultaneously renders it weak to common types (Grass, Water, Ice, Dark, Ghost, Bug), has some respectable bulk, and is better for its utility than its offensive prowess.
Claydol @ Leftovers
EVs: 248 HP / 8 SpA / 252 SpD
IVs: 0 Atk
– Stealth Rock
– Rapid Spin
– Earth Power
There are a number of ways to go about this set, but this is the one I prefer. The general idea is to get up Stealth Rock and Rapid Spin whenever necessary. This particular implementation of the set uses Toxic to wear down walls that can take its Earth Power with ease, and Earth Power is to chip away at Pokémon who don’t mind Toxic. You could run Psyshock or Ice Beam over Toxic, but Claydol’s offenses are so lackluster. (Ice Beam does 2HKO 248/8 Eviolite Gligar, though.) You could also go physical, using Earthquake and either Zen Headbutt or Stone Edge, but both of the latter moves are unreliable with their chance to miss. Besides, Pokémon susceptible to Ground are generally physically defensive (read: Drapion, Durant).
There are many ways to go about EVing this set; Pokémon Showdown suggests a spread of 240 HP, 12 Def, and 252 SpD. You could use this build, that build, or go physically defensive depending on your team’s needs. Heck, you could even try Modest or Adamant offensive if you so desire. (I wouldn’t recommend it, though.)
As mentioned before, Claydol has other utility options in dual screens and Trick Room, as well as an interesting offensive movepool. Magic Coat is also something worth bringing up, as it can reflect things like Taunt, hazards, and Toxic that can bother Claydol (or the rest of the team, in the case of hazards). With this, it brings to mind a number of sets: Light Clay dual screens with dual STAB (or possibly Magic Coat), Trick Room with Macho Brace, offensive Calm Mind, Choice Specs with Trick, and Rest+Sleep Talk, just to name a few. However, these sets are gimmicky and/or outclassed; Cresselia is a better dual screener and attacker, Bronzor is a better Trick Room user, and Gastrodon is a better Ground-type bulky attacker (although it can’t set up in any way). In a nutshell, Claydol is known for its utility—nothing more, nothing less.
http://pastebin.com/KDpCLu0g (note that this is a SAMPLE and should thusly be treated as such)