We all know'em, they work. But the problem that I have with them, is they ****.
I have slowly but surely been eliminating these from my place of employment. The problem with them is that when you are using stranded conductors, the mere application of these little buggers damages the conductors 9 times out of 10. And then, most of the time, some part or another of the conductor is showing bare - so people will wrap them up with electrical tape. Have you ever tried to unwind electrical tape that's been in a large motor's junction box for a couple years?
The solution? Awesome wire nuts.
These things fit up to 12 AWG and as small as 28 AWG, rated up to 600 volts, 20 amps, AND have a built-in test point. It's also got a strip gauge right on it so you get the right length, first try. The levers snap open, slide the wire in, snap it shut. You can remove one conductor and leave the other one totally connected, you never disturb the mechanical connection of the original conductor. Also the one you remove is preserved, so you don't consume precious conductor length on things like motor housings.
I know I sound like a salesman, but I love these things so much that I carry a handful of them around in my toolsack and whenever I see a wire nut I replace it with a Wago.
Check it out here, buy some here, and then come back and tell me how you like them