Mostly my SO long handled double box wrenches or SO pliers, but when i bring a new Snap On tool or two in and he see's me bring them to my toolbox, he'll say "Oh nice to know if i need one of those i can borrow them sometime".

. Not only does he always ask to borrow, but he also routinely steals tools if you leave your box unlocked, or takes some of shops tools.
Well,,, We need to give you some grumpy old fart lessons!!
he says:
" Oh nice to know if I need one of those I can borrow them sometime"
One Possible Response:
Oh ya sure ya betch ya ,,, This is $XXXX, that is too damn rich for your taste;;;; If you are too damn cheap to buy your own; you sure as heck would be too cheap to replace this one if you lost it or screwed it up..
or:
Yes, It is a $XXXX tool; but it has a glitch that you will not like; it is allergic to freeloaders...
or:
Snappy has one for you on the truck, If you need one you can still catch him,,,,, better run!
or:
They got your version at Harbor Freight
or:
Dream on!!
or:
Screw that noise
or:
If you needed one, you would have owned one by now
or:
You might have to cut into your drinking and smoking money and buy one
or:
no, I am going to break my bad habit of loaning out tools...
or:
no
Take your pick,, but remember one thing: words can be like emotional bullets, so don't use unnecessary force... pick your battles wisely.... But stand up for YOURSELF....
It is not totally uncommon for experienced technicians with years of experience and loaded toolboxes to occasionally loan out or borrow a specific tool or different brand of tool from each other.... I rather DOUBT that this would describe your situation....