Our favourite little bug got Trick and Sucker Punch. Much of it hasn't changed, but I have added some changes and the Trick set and made some changes. No need to change Opinion / Counters, at least not as far as I can see.
www.smogon.com/dp/pokemon/shedinja/
[SET]
name: Swords Dance
move 1: Swords Dance
move 2: X-Scissor
move 3: Shadow Sneak / Sucker Punch
move 4: Will-O-Wisp / Toxic
item: Focus Sash / Lum Berry
nature: Adamant
evs: 252 Atk / 4 Def / 252 Spe
[SET COMMENTS]
<p>This set takes advantage of Shedinja's only decent stat, Attack, and aims to increase it to higher levels courtesy of Swords Dance. Because of Shedinja's various immunities, it can often manage to pull off a Swords Dance or two, hopefully causing problems for the opponent before switching out. X-Scissor is a good STAB move, and makes use of Swords Dance well. Shadow Sneak is a weaker move with STAB and has a stage one priority. However, Sucker Punch may be used for its higher base power over Shadow Sneak, and will hit Normal-types (scoring an OHKO on Swellow for example), but it is much less reliable.</p>
<p>Due to Shedinja's limited movepool, a status move, either Toxic or Will-O-Wisp makes an appearance to cripple any incoming pokemon that might be carrying a super effective attack. Toxic is generally the superior move against walls that carry a move capable of swatting Shedinja while Will-O-Wisp can effectively neuter any physical threat including what is arguably, Shedinja's greatest threat; Pursuit-users such as Metagross and Scizor.</p>
[SET]
name: Trick
move 1: Trick
move 2: X-Scissor
move 3: Shadow Sneak / Sucker Punch
move 4: Aerial Ace / Will-O-Wisp / Swords Dance
item: Choice Band
nature: Adamant
evs: 252 Atk / 4 Def / 252 Spe
[SET COMMENTS]
<p>Shedinja with Trick can be quite a surprise, and can really stop the opponent's Pokémon. Trick means you can cripple many of its common switch-ins. Heatran and Skarmory won't enjoy Choice Band, nor will Giratina in Ubers. While it doesn't stop them using super effective attacks on Shedinja, it makes them much more predictable, and easy to play around. X-Scissor provides a STAB move that will hurt a few Pokémon when Choice Band is attached, and can be utilized after. Shadow Sneak is again, a reliable move but it falls short of a guarunteed OHKO on Gengar and Azelf when Shedinja holds Choice Band, something Sucker Punch will manage.</p>
<p>The last slot depends on what you need. Aerial Ace will hammer any Heracross coming in for a Guts boost, Pursuiting Shedinja away. Will-o-Wisp gives Shedinja the opportunity to threaten the opponent even more, Tricking one Pokémon then Will-O-Wisping the next switch in. However, Swords Dance can be useful after Trick, and it will offer Shedinja more of a chance of sweeping.</p>
<p>Even though it may seem a gimmick, Protect can also be used on this set. It works brilliantly well in conjunction with Trick, as it furthermore makes it easier to switch in a team mate to counter the opponent. It also means that Shedinja will be able to see if the opponent is predicting a switch and doesn't use a super effective move, which means Shedinja can then stay in with impunity until they switch, due to the choice item.</p>
[SET]
name: Baton Pass
move 1: Baton Pass
move 2: Toxic / Will-O-Wisp
move 3: Heal Block
move 4: Shadow Sneak / X-Scissor / Sucker Punch
item: Focus Sash
nature: Jolly
evs: 252 Atk / 252 Spe / 4 Def
[SET COMMENTS]
<p>Even with nothing to pass, Baton Pass is a completely viable move on Shedinja as it allows it to scout for counters, and also the chance to offer a safe switch-in for a team mate, giving you a more favourable match up.</p>
<p>Toxic is a good way for Shedinja to cause damage, without it, Shedinja may struggle outside of using entry hazards, causing damage due to Shedinja's knack for forcing switches. Heal Block with Toxic means the opponent cannot use Rest or any other healing more, and therefore cannot stall Shedinja out of PP.</p>
<p>However, Poison or Steel-type Pokémon, as well as those with the Immunity ability, will be unaffected by Toxic, effectively stopping Shedinja cold. With Baton Pass, Shedinja can immediately retreat and bring in a suitable counter for free, such as Dugtrio or Magnezone. This pair can come in handy as Magnezone can trap and kill most Steel-types, while Dugtrio's STAB Earthquake hits Poison and Steel-types for super effective damage.</p>
<p>Will-O-Wisp is an option over Toxic for the aforementioned Steel and Poison-types but the process will be much longer and more arduous as a burn's damage is constant. However any offensive move, particularly Shadow Sneak, Sucker Punch or X-Scissor may be used in its place if you are afraid of Taunt. Even specialized Hidden Powers can be used to deal damage to specific users of Taunt (such as Hidden Power Electric for Gyarados).</p>
[Other Options]
<p>Shedinja has a couple of other nifty tools at hand, but many of these are situational.</p>
<p>Natural Gift with the appropriate berry is a very workable option for Shedinja, considering its limited movepool. For example, Natural Gift with a Ganlon Berry is almost a guaranteed OHKO on an incoming no HP / Defense Rayquaza, provided that you predict correctly. However, this means it won't be able to hold a Lum Berry or Focus Sash, meaning that it will only be likely to work as Rayquaza switches in to Shedinja.</p>
<p>Protect can also work on other sets bar Trick, although generally there are better options. It means Shedinja can scout for moves that would otherwise be fatal to it, and works nicely in tandem with Will-O-Wisp or Toxic, to quickly reduce the opponent's health.</p>
<p>Bug Bite can ruin any Pokémon planning on using pinch berries, especially in Ubers where it is commonly used.</p>
<p>With a Jolly nature, Shedinja achieves enough Speed to make use of Agility. From this point on it can attempt to sweep, or it can Grudge away one important attack. Note that Shedinja can only have Agility, Swords Dance, OR Baton Pass on a set at the same time. Any combination of the three is impossible to obtain and is therefore illegal.</p>
[EVs]
<p>Due to Shedinja having 1 HP, most of the time you will be using Attack, Special Attack, or Speed EVs. Generally, you shouldn't be using special attacks on Shedinja, so maxing out Attack and Speed EVs is all but required. The extra 4 EVs should go into one of the defenses to strengthen a Baton Passed Substitute.</p>