I want to rework Shaco, here's what I want to do.

Total Rework: His passive and ultimate. Changed: Jack in the Box. Tweaked: Two Shivs Poison. Largely unchanged: Deceive.

First off, Deceive. I'd like to clean up the cast animation so there's no delay when casting. When you hit Q he immediately disappears into a puff of smoke. Right now there's a very short cast animation/delay.

Next up: His passive and Two Shivs Poison because the changes here are related. I'd like Shaco's passive to be a stacking debuff that slows. How many times and the % slow would be subject to balance, but it should be enough that Shaco can stick to an enemy and get in a few basic attacks in while doing it. Each stack could have a different additional effect (slow, vision of target, grievous wound, -AR/MR debuff), increase the slow, or just be another stack, the important part is that it stacks. Two shivs poison's passive gets removed (the slow is now on Shaco's passive so we don't need it here anymore) and instead the active gains a %hp execute that gets more powerful based on the target's passive stacks and also cleanses all the stacks off the target.

Jack in the Box: Cut Shaco down to either 1, 2, or 3 total boxes (the way Caitlyn traps are limited). When a trap triggers it does damage over time in an AoE and silences. After a duration or when the box is destroyed (takes damage like Zyra plants.) the DoT and silence end. The major trade-off here is that Shaco can't make box nests like he used to and the boxes only stops casting (stopping blinks, dashes, and jumps though), but he gets more powerful and resilient boxes. Also triggered boxes give a trinket ward sized vision area.

Hallucinate: "An imaginary knife will kill you if you believe it. A real knife will kill you whether you believe it or not." Shaco creates a Hallucination of himself into target opponent's mind (or enemies in an AoE, or just all enemy champions globally) that echos Shaco's damage again 0.25 or 0.5 (this depends on balance) seconds after Shaco inflicts it. If the hallucination does not deal damage to a target for 2 second, the target begins regenerating the damage dealt by the hallucination. The hallucination deals some percentage of the damage that Shaco does and it takes enemies 2 seconds to regenerate the damage it deals. The ability itself should last something like 4-5 seconds. The idea being that with a percent damage bonus and execute, Shaco should be able to assassinate someone. The time delay means he can do it fast, but not instantly and it's a risk because if he fails to get the kill his target gets a bunch of their life back. He'd lose some ult shenanigans in exchange for a more consistent ult and better assassin style team-fight.

Assuming that JitB and 2SP both retain some AP scaling, and I don't know why they couldn't, Shaco could still build AP or AD. His ult's damage echo would trigger off magic and physical damage.

Balance considerations: Allowing his Q and/or R to reset on kill or assist, or increasing the ult's duration on kill or assist. How Two Shivs Poison's execute damage interacts with the hallucination. (Does it include the execute damage from the first shiv, or does it do it's own execute damage based on the stacks applied in the 0.5 seconds after the first shiv hit.) I've left a bunch of damage numbers off because I could only reliably figure those out if I had access to a Riot test environment that I could play with.