I use chenille stems with a drop of TriFlow on it - they're bendable, so you can reach around in tiny places.
I am a Harbor Freight junkie.
The last time I was there, I got a bunch of ratchet clamps for $1.00 each. They're meant to hold things together, or clamp something down to a tabletop. I'm going to use mine as a "fence" the next time I'm quilting - apply them to the edge of the table to keep the puddled-up quilt from sliding off the table.
Those magnetic pin dishes are the bomb for holding pins or parts - and if you have to take the tiny screws out of your bobbin case, do it over one of these empty dishes so the screw won't get lost.
The wand magnets are a must have. (For when you take the screws out of your bobbin case without something underneath that will catch the screw.
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A mechanic's stethoscope, so when you're refurbing an old machine, you can pinpoint the source of a grinding noise or a click or a thump.
Acid brushes for scrubbing with acetone or denatured alcohol. I usually cut the bristles down on these to make them "scrubbier."
HF is such a great place!