Very tricky!
I think that most used and most loved are two different ones in my workshop. And, of course, it depends on how you define a jig.
I shall take it to mean a shop-made gadget that is used in conjunction with a tool or a machine to make the job quicker, safer, easier or more accurate than I can do by hand. Will that do?
In that case, my most used is my short rip fence. I never rip anything without it, and it also doubles as a handy store for spanners, spare arbour and that sort of thing related to the saw.
Most loved has to be my Ultimate Tablesaw Tenon Jig. Although I made it some years ago (I need to remake it, it's got a bit damaged in the last few years) I still get a kick out of seeing my tenons fit exactly time after time, and knowing that there will be no clean-up necessary afterwards. When I die I know I have left something good behind. OK, it may not be much for a whole life, but it is my offering.
That picture looks a bit untidy because the workpiece is too large for just the toggle clamp which is part of the jig, and I've had to use a trigger clamp as well.
But this is why I love it:
Today I am using my
Domino support jig, very pleased with that one too.