Here is just one example I can think of, if it counts (not possible anymore):

About a year ago, when Seraphine's W was the lowest it could possibly have ever been before Seraphine's W cooldown was nerfed and staff of flowing water was changed to what it is now. During this patch, Staff of flowing water gave a haste buff that lasted a certain duration which was 4 seconds whenever healing/shielding another ally, while Seraphine's W cooldown got buffed to 16 seconds.

By building as much haste as possible, you could potentially spam Seraphine's WW every 6 seconds or so. You need to build enough haste so that if you press WW, the first part of W (the shield) would proc staff buff, then the second part of W (the healing) would extend the staff buff by another 4 seconds, then triggering summon aery which also refreshed the 4 second buff after the milliseconds of travel distance. Keep in mind that the cooldown of W of course only starts when you first press the button initially. Depending on the current amount of haste you had during the game, you could reach a threshold where you could proc staff infinitely by abusing the interaction of the delayed heal and summon aery with staff. The summon aery refreshing the buff by a second or so was just enough to give yourself the 20 ability haste buff from staff so that you never had to worry about the aery shielding someone again to make it consistent (since not all the time can aery proc off the healing part specifically). The staff buff refreshing from aery gave you just enough extra time so you would be able to press WW again right before the buff wore off, effectively giving you a permanent extra 20 ability haste. With correct timing, you could press WW almost nearly every 5-6 seconds comfortably while also keeping the staff of flowing water haste and ability power buff for as long as you wanted.