Fire extinguisher next to each point of egress. A lot of people place it next to where they think a fire will occur, but that's exactly the place you'll be trying to escape if a fire does break out. No batteries ever get left charging overnight. They charge while I'm there ONLY.
Safety glasses on or near every piece of equipment that requires a pair (grinder stand, table saw, miter saw, etc.). I throw out or polish the lenses on them when they get scratched. I don't want to be tempted to work without them "just this once" if they're hazy or hard to see through. A headlight polishing buff and a bottle of Meguiar's compound (forget which one) does a good job on them. If the scratches are deep, they get tossed. I keep a couple still in the blister packs as replacements.
Nitrile gloves plus a good set of snug-fitting work gloves (like Mechanix or equivalent). I have a bunch of the loose old cowhide work gloves but I hate wearing them and only do it when I'm pretty sure I'll ruin a set of gloves. Loose gloves get caught on stuff.
Box full of dust masks (I buy them in 20-packs). Wood dust and I don't get along.
Hearing protection. I have 5 pairs of earmuffs. I usually put a pair on when I go into the shop to keep me from having to hear the compressor run. I'm at the point where I won't do any loud job without earmuffs, no matter how short. I won't even cut a single 2x4 on the miter saw. After years of working on stuff, loud sounds just annoy the hell out of me anymore.
Full face shield hanging near the grinders.
I don't have a first aid kit in the garage, because if I do something where I need the first aid kit, I also need to go in the house and wash out the cut or whatever. I do keep a bottle of rubbing alcohol with a pump sprayer head on it for cleaning up circuit boards, and if I cut myself and can't get to a sink right away, I'll give the open cut a shot. Yeah, it stings, but it goes away pretty fast.
Floor squeegee. I hate slipping on antifreeze, and in a shop, a slip could land you on something sharp or moving. Another pet peeve is having sawdust or wood cutoffs underfoot, especially when running the table saw. I sweep up the sawdust and keep some to soak up spills.
Take the garbage out frequently. I never leave any paper towels in the shop if they've been soaked in oil, alcohol, brake cleaner, etc. The garbage gets taken out every time I'm in the shop. Garbage bags are cheap, garages aren't.
Many, many razor and utility knife blades. I change them out the second they get dull. Blades too dull to cut cardboard are more than sharp enough to cut skin.
JACKSTANDS. NEVER trust a jack. Also wood cribbing, because sometimes you shouldn't trust jackstands, either.