Most used ones are 4, this Philips PM2811. Current shows -0.03 but that is fixed to at this moment.
Modified 1974 electuur powersupply :
The most cute:
Modified Delta 30V 10A
Besides that I have psus up to 2000VDC ( but they are 1 to 5 mA), a huge 50kilo box with no terminals but a few fixed (-6,12,18V and can be coupled to get for instance 24V by using -6 and 18. powerrails. Ex army, no clue about the amps but it should be very high, the former owner powered all his green transmitters and reciveivers from this one supply.
This is my "mean machine" own design dynmic load to get constant current, can do over 10A and about 30V if I want. There is a LM317 to set the voltage for the gates of 3 HEXFETs, the load is also 3 of those IFRZ256 the electronics regulate the voltage on top of the load. So it compenstates the coltdrop over the current regulator. It can be used as dynamic load or for instance pulsating battery charger. The ugly cabinet was an old French noise generator. Stil worked but it was not very usefull. Pronably some jammer. It had in a test over 1000V output in a load and with only a short pin in my SA as antenna it was full screen beyond 1GHz. I use it a lot to cycle my back up batteries in my lab