This is a simple "Plume" sprinkler / myster / water blaster thingie.
Gives nice coverage even at low pressure, more of a mist than droplets. Can be used as a hand watering tool too, or even as a "crazy blaster" by putting it on the end of a piece of hose (maybe someone remembers that toy from the 80s..)
Check out the video to see it in action: https://www.youtube.com/watch?v=61ljK4m30XE
Based on the great design "Noch ein Regner" by 3DPNoob, but redesigned to print in one piece (no assembly), with the Gardena connector from the "Pilzregner", which worked well for me. (Both from Thingiverse)
The model has some tricks to fools slicers into doing the right thing, so the maximum layer height I'd recommend is 0.24mm. Tested in Cura and Slic3r Prusa, if using Cura, uncheck "Ignore small Z gaps". For PLA, I found it needs at least 3 or 4 perimeters, otherwise it leaks between the layers. Should be printed without supports.
There's two versions, one with the Gardena type connector, for which you'll need an O ring which you can scavenge off a Gardena fitting or buy. The other version has a 3/4 British thread (not tested yet..).
I originally posted this on Thigiverse, but I've decided to add everything here too since Thingiverse seems to just get worse...
The author hasn't provided the model origin yet.