I also tend to let others use all of my tools ....with the appropriate death threats
for some ot them. But that is usually done in a "use this during this class time and give it back at the end" situation.
When I travel to give demonstration type workshops and when I'm away at artist-in-residence programs and such, I usually do not bring my "usual" regular use studio tools. I have the "B" set of tools for that purpose............just in case stuff gets lost (or TSA confiscates them).
In the real "favorite stuff" do-not-want-to-lose department:
I have an oak rib that I made way back in undergrad school.
I have a rope-wrapped paddle that I made while working at my first real professional studio in 72.
I made a large fude-style horsehair brush out of palimino tail hair years ago that is great.
One particular 4" long section of whipped rope (used for texturing).
I have a hanko-style signature stamp of stone that I carved in Japan in 1996 (with the help of a Japanese potter there and liberal applications of sake).
I have some bamboo glaze pouring ladles that I brough back from Japan years ago.
One particular size and shape of trimming kanna that I buy in Mashiko, Japan that I cannot find anywhere else (I stock up spares when I am there).
Can't think of anything else right now, off hand... but I am not in the studio to get my feeble old brian refreshed.