A simple stand/holder for a cheap&popular pulsing LED heart kit, for assembling it yourself. A cool gift idea if you offer someone to teach them basics of electronics and how to solder, so that they can keep the result. Also a decent scenario for a date ;)
There is a square hole for power wires. I suggest using a cheap generic USB cable for connecting it to an old weak charger or a PC/laptop port.

Hardware needed: 1x regular M3 nut, 1x M3x12mm screw with countersunk head

Printing: 0.2-0.3 layers, 10-15% infill, 1.2mm perimeter thickness (3 for 0.4 nozzle, 2 for 0.6). No supports needed. Print the stand part on the side, everything else just on the biggest flat bottom.
The diffuser middle has just one 0.3mm layer, print it with some translucent filament. I suggest using a nonstandard infill pattern on the diffuser - archimedian chords and octagram spiral look best IMO. A combination of fluorescent filament and UV LEDs may also look nice. There are 2 versions - with and without holes for potentiometer and switch. ! Make sure the perimeter and infill on the first layer are fully connected without gaps, tune the overlap or flow% for best result.

Some parts are press-fit into each other. Needed tolerances will be different for each machine, but i got good results on 0.6mm nozzle with the following ones in the models:
PCB-holder - 0.3mm, PCB clicks in place, but can be pushed or pried out
Stand-base- 0.12mm, stand can be inserted with a bit of force, but then stays put without the need for glue or fasteners
Diffuser-holder - 0.15mm, fairly tight fit so it doesn't fall off, but can still be pulled off
M3 nut - stand - 0.25mm, you can use a screw to press it in place
Print at slightly smaller/bigger % scale if having issues.

Assembly: Assemble the PCB and cut component leads, insert the stand into the base, press the M3 nut into the stand, attach holder to stand with a screw, cover the screw head with 2-3 layers of thick electrical tape so it doesn't short any contacts, press the diffuser onto the holder. Enjoy!

Note - you might want to dim the LEDs so that this thing doesn't hurt your eyes in the dark, as it is fairly bright. Replace 22R resistor with 33, 47, or 68 Ohm. LEDs with diffused lenses look better. Regular transparent 3mm LEDs are used in the photos.

PCB schematic and layout (remade in EasyEDA) also provided just in case someone wants to make a different shape.