Is Runaan's Hurricane worth it on Kennen or Caitlyn?

Runaan's Hurricane, if it hits extra targets, counts as hits for Kennen's W passive and Caitlyn's headshot passive. This increases the frequency of stuns and extra damage on both champions. You also get a 70% attack speed bonus from the item. Typically, hurricane is not seen as viable. But in these cases, is it worth getting over other items?

Solution 1:

Runaan's Hurricane is an extremely niche item and only useful on a small handful of champs.

In your case, I would never before have even thought about getting Runaan's on Kennen. It can work if you want it to but in my opinion you would be better off building more damage (assuming AP over AD here). Kennen just feels much more spell based than auto-attack based, which is why you should build more damage for spells.

As for Caitlyn, I feel she's one of those handful of champs that can really use this item well. As an ADC, of course she will be continuously auto-attacking the other team and getting her passive off every other shot would be a huge boost in damage. Even though it would be useful, it's not useful to the point where I would ever rush this item. It would probably be the third of fourth (including boots) after Infinity Edge, Blood Thirster and possibly a Phantom dancer as well.

As a side note here is some other champs I feel make use of Runaan's:

• Ashe, Constant AoE slow with her Frost Shot toggled on. Pretty much the same as a shorter cooldown Volley with less damage and no cooldown except attack speed.
• Graves (to some extent), it works the same as it does with Kennen and Caitlyn lowering the CD of Quick Draw faster.
• Kog'Maw, lots of %hp damage on every attack.
• Teemo, poison for everybody!
• Twitch, True damage poison for everybody, then use Expunge for huge AoE damage.
• Varus, Spread around Blighted Quiver for the bonus magic damage then snipe em all for lots of % hp damage.

Runaan's can also work well with both Black Cleaver and Blade of the Ruined King since it will apply on-hit effects from both.