In my Leatherman's. A SwissTool ratchet is soon to be ordered; along with the Plus sheath and other extra goodies it comes with. Think my next Swiss Knife Shop order will mostly comprise of the ratchet, the "L" wrench, the rubber holster (as it can be cleaned easily), the corkscrew, and the "Plus" sheath.
T6/T8. This is for folders, as I lose those tiny bits so often, it ain't funny. And it's always either the tamperproof T10 (LM), T6, or T8 bits.
T27/T30. Most Stihl equipment is held together with a T27 Screw.
T15? I think.
I need to ditch the two hex bits in my "Removable Bit Adapter" for Torx. We have more folding hex key sets around here than I can count; so I'm never in need of a particular hex bit and don't have it.