Mine is quite possibly my Alpkit Gourdon 20 litre day sack / drybag. Its my usual walking sack all year round these days and is light enough for challenge events where you might be moving fast so want something very light (600g it weighs). Its not really my favourite but its the one thing that gets used most I reckon.
My favourites are probably the stuff I like but don't really use. Kinda like you see something and think "hey1 That's cool!". So you get it and never actually use it much if at all. I think for me the honey stove is like that. Also I know I want an mkettle and Evernew DX stove kit with the evernew burner and the trivet too from BPL-UK. I know they are cool kit and I want them and they would immediately become my favourite kit but I also know that my go to stove will always be the little primus micron with reliable PZ ignition. So light and has never, ever let me down. Why can't I see this as my favourite? I think it could be that the others have fire in them that is fuelled by wood!! If primus ever made a light stove that you fed wood into and out came gas for the burner I am sure that would be the only way I'd make a primus gas stove my favourite. It is purely functional without any extras like interesting orange flames to watch.
I once had a long discussion over art vs artifice. What it was about we were sitting outside a pub where there were railings on the river edge. They were decorated. The railings were functional so were artifice but it had decoration which was unnecessary to the function. That meant the railings were art as much as function. You could have put cheap scaffolding poles in and it would have had the same function being met. I think with my favourites it is a degree of the unecessary to them that grabs my attention. If that makes sense. Another drunken pub conversation that doesn't make sense sober no matter how much you try to justify it.