This build can be used for single battles, but for maximum effect, double battles are the best. Ability doesn't matter, but high IVs in def and spec def, as well as a fast trick room backup are a must. Turn 1: my speed tricker uses trick room, shuckle uses power trick. because shuckle is slowest Pokemon in game (with like 5 base, 0 IVs in speed and 0 Evs, my shuckle has single digit speed), shuckle will go last with power trick, thus all but ensuring that shuckle is not killed. Then shuckle can spam the rock slide/sludge wave/earthquake until other team dies. If you feel threatened by priority moves, make a substitute before you do power trick. Trick room will last for 5 turns. Most teams die in 3/4. (well most die in one cause they ragequit, but hell, I'm not counting the morons.) Some protect users have been able to outlast the trick room, but because they were so focussed on protecting themselves, they couldn't kill either my first trick roomer or my second. So: moves.
1: Power trick
3: Earthquake/Rock slide/Sludge wave (Earthquake because...Earthquake, Rock slide = instakill STAB, sludge wave because...I like poisons
4: either another wave move or my personal favorite...poison sting. why? BECAUSE I KILLED YOUR LEVEL 100 RAYQUAZA IN ONE HIT WITH A SHUCKLE USING POISON STING! THAT'S WHY! AND IF SPLASH DID ANY DAMAGE, I'D USE THAT INSTEAD!
needless to say, I only actually use poison sting if you only have 1 or 2 Pokemon left, and if I feel like rubbing your face in it.
Unlike a lot of sweeping/trick room strategies, this one only requires one turn of buildup, and unless they can outspeed and 1 hit your trick room guy...its over. Game over, man. Game over. Shuckle should be in the ubers, but until they fix it, I am one of only a few, apparently, who has seen shuckle's sheer potential for a competitive team. I also use two wall shuckles in a real battle, both with 31 IVs and max EVs in def and spec def.
My wall build is as follows. (without contrary) needless to say, max EVs on def and spec def.
1: Toxic. (Do I really need to explain why?)
2: Protect The best single use stalling move
3: Double Team/Safeguard for making shuckle all but impossible to kill, or making it impossible to wear him down safely
4: Rest(if you have a Lum/chesto berry equipped) or Sandstorm to deal that little bit of extra damage
1: Toxic(hey, I like poisons!)
2: Shell smash Great when trolling an attack team, for reasons of the next move. or Gastro acid if with one of the greatest tanks of all time Slacking in a double battle. Otherwise put rest here.
3: Either Power split or Sandstorm goes here. Sandstorm helps Shuckle by dealing extra damage, although that may help your enemy if they have a Tyranitar or something of that sort with an evade boost.
4: Rest goes here if you don't have it already, otherwise put protect
so to recap, either
item: Sleep healing berry (Lum or Chesto)
2: Shell smash
3: Power split
item: Sleep healing berry (lum/chesto)
2: Gastro acid
Note: alternatively, you could forgo rest and put both attract and a leftovers on him, but its rather unreliable. I've played tournaments with over 200 people and won with my shuckles, so I would know.