CriesToMyEgirls, OCE Silver 4. For detailed matchup win-rates click the link below.
[https://i.imgur.com/4nIsRsa.png]

Warning: My take on Shaco is my purely subjective opinion in "low-elo" over hundreds of games.

So once upon a time I was looking for a "braindead" pick who I could pick and not int on. Shaco's tools for tormenting enemies and escaping with Q-Auto/E slows, W peel and R damage and cc was a perfect fit for me. With my playstyle, flash is always better than exhaust, as with exhaust, you rely on your teammates more. Shaco's supporting and kiting playstyle was also optimal for lag and perhaps a little slow reaction-time on my part.

One of Shaco's main objectives is to die less than every other player in the game. This is due to the nerfed AP-ratios and therefore lower carry potential when compared to other champions (Trading kills is not always worth it.)

Shaco has many tools to avoid dying.
Raw Stats: He has high base-MS despite his MS nerf. High base healing. Self-Peel.

Pink ward once said something along the lines of: Shaco has the unique role of being a supporting assassin. This is absolutely true! You need kills but it's "okay" for hypercarries like Master Yi to take a kill or two ("Supporting" Assassin).

Champions with mobility have better dueling with Shaco. Many top-laners require to be attacking you for them to heal or gain free extra damage with conqueror, Shaco solves this by pressing Q.

There is a lot of information in the Threats section. One thing Shaco doesn't like are Machine guns with peel (Ashe/Aphelios/Senna/Jinx) and Shaco hates machine guns with mobility (Lucian/Caitlyn) this is why I opt for top lane over AP Shaco support. As well as the fact you must rely on your ADC somewhat.

Since your role is a supporting assassin, healing supports are your main counter (Soraka/Yuumi), as well as self-healing + Damage (Aatrox). Shaco can do well into tanky opponents.

One thing to note about Shaco is his empowered autos. To do this, you Q/Q-then move behind an enemy and auto. This is very important for Shaco's DPS. To avoid taking return damage, simply do the combo Q-W-auto-E-move away/finish them with ignite. Shaco's AP ratios/damage was nerfed during season 11, therefore this puts an onus on you to utilize all of Shaco's damage sources for maximum kill efficiency. Although it doesn't do tons of damage, practice including it in your combo, especially if you need more damage than an E-Ignite. One downside of an Q-auto-E-Ignite combo is if they flash out of vision/out of range before you cast E. (E-cast is not as instant as an ADC's auto-attack).

This brings me to timing with Shaco's abilities. When you place W, there is a short period of time before the W activates and begins shooting, even if you place it directly under an enemy. This is one of the reasons kiting with Shaco is important.

In certain matchups and under limited conditions AP Shaco mid and AP Shaco support may work, however to me it is less consistent than AP Shaco Top. FYI my current go-to champion if Shaco is banned is "braindead" Full Damage Sett which has many similarities to Shaco. Although, in the end, The Demon Jester is my most successful champion.

One thing Shaco and Sett have in common are "being a chad" or "playing the tough guy" to bait enemies into making mistakes. Notoriously, the Shaco worm-dance or the Sett sit-ups are used as the ultimate bait tool. Also, walking toward your enemies in a weak position, then walking away and somehow surviving your opponents damage. This is due to Sett's W being quite strong and buying him time, much like Shaco's ultimate, Ws and especially his Q. However, in my opinion the Shaco Q makes Sett's BMing look like compliments. Literally, you can walk toward your enemy at low-hp and bait summoners, abilities or just plain tilt the enemy. To frustrate them, Q right before they channel/cast damage that kills you. One example of channeling damage that kills you is Aphelios' long range "mark" or Rengar's Ult or Caitlyn's Ult. Once these are channeled/activated, you can die within a short period of time, even if you Q away so be aware of this when BMing your opponents. One of the worst examples of channeling damage is an auto from an ADC/ranged champion, once it's activated/marked on you, Q cannot stop it, perhaps Zhonyas can, but above bronze, you have no damage if you go Zhonyas. Just take the death and learn from your underestimation of ranged champions.

Penetration... Penetration gives The Demon Jester Peace of mind. He loves penetration and tries it every chance he can, it makes him feel good. Shaco's AP ratios have had 2 nerfs so far this season, this has increased the utility of flat and even percent MAGIC penetration (Not what you were thinking!) as opposed to raw ability power. Even late game, the AP ratios on Shaco are so lackluster you could build a tank item (Abyssal Mask) and get more damage (15% damage increase) for your gold than AP items.