Curious as to what we're using these days. I started off in the hobby using Meth Blue, but learned a lot of different things over the years, but with the new meds out for fish, I'm sure that many of us now have our 'favorites' that we keep on hand and use.
I use Formalin II as a 'tonic' after water changes, and particularly with wild specimens or new imports, and that seems to help things.

I have been lucky so far and have not had any reason to use medications in a while. I aquire most of my fish from small breeders and I think this help a lot to keep new diseases from getting in my tanks. The few times I did have problems was when I got fish from the petstores. Needless to say I do not put any fish in my fish room that come from overseas or the petstore. In my other tanks however I have had a few problems with ick in the past, I can not remember what type of ick treatment it was but I got it at petsmart. I believe it had malachite green in it though since it turned the water green. With all of this said I guess I should knock on wood.

I like to have a stocked medicine cabinet.

My preferred antibiotics are kanamycin and metronidazole, followed by tetracycline as a distant second choice (it's less effective in hard water). I typically don't do bath treatments tho unless the fish aren't eating as I prefer to make up a medicated gel food
http://thegab.org/Articles/MedicatedGelFood.html
for a bath treatment, maracyn plus is good as is kanamycin and metronidazole (depending on symptoms).

For external parasites, I keep formalin and quick cure on hand and praziquantel for flukes.

I keep salt on hand, but only recommend it for specific things (e.g. preventing nitrIte poisoining or treating ich since ich is likely not salt resistant), however, some external parasites will not respond to salt these days. Noga identified several strains of costia that can tolerate salt.

Potassium permanganate for disinfecting things or as a shotgun treatment with the biofilter pulled if I'm not sure what's going on just to knock whatever back while I figure out what the problem is.

finquel (MS222) for sedating or euthanizing fish.

Most times, I do quarantine new fish and I always disinfect new plants.

Do you guys ever use a microscope to identify what's bugging your fish?

Actually I did buy a microscope from my local hobby shop a few months ago. It has a digital camera on it that you can plug into a usb port. The picture quality is not the best but for $80.00 guess you can not expect too much. It was actually the best one I could find without paying a few hundred dollars.

My favorites are Melafix and Pimafix. However, I have used others in the past. Once I used a copper treatment to treat one of my saltwater fish for Ick. (the one that is a live parasite) It worked well but, I forgot to clean the fish of copper and I ended up killing all my invertebrates!

Miroscopes have come SUCH long way since I got mine at 8 years old; and used it until a decade or so ago. Having them connect to USB's so photos can be made, and for easier comparisons is so much easier these days. And sometimes there are some interesting things to see...

I use 1/8 to 1/4 teaspoon neomycin powder(obtained through
my vet) and Fungus Cure from Aquarium Pharmaceuticals. Quarantine the fish usually in a 5 and leave there for a week. Works fairly well for clamped fins and general "not looking too good"

Shadow.I've been watching the new products for backyard pond care grow,especially medications.I especially like two products.The first is Jungle's Pond Anchors Away.This works on Anchor Worms and other Perasites,it contains Diflubenzuron.The second product is Metro Med Rx ,this contains Metronidazole and eliminates deadly tape worms.This is a high quality fish food medication.It comes in pellet form.I feed it straight out of the bag to my swords and platys but I like to grind it to a fine powder for my show guppies.

so are you talking about metromeds?
https://www.pondrx.com/products/16159.html
or something else?

The metromeds from the link above contains: Metronidazole, Ormetoprim-sulfa and Oxytetracycline
metronidazole hits some protozoans and anaerobic bacteria and has the side effect of reducing GI irritability.
Ormetoprim-sulfa is a potentiated sulfa antibiotic and
Oxytetracycline is also an antibiotic that hits mainly gram negative bacteria. It won't touch tapeworms.

Diflubenzuron only kills parasites that have chiton in their exoskeleton. It keeps them from being able to molt. It won't touch most common external protozoan or monogean parasites (flukes).

Michael: so what magnification and how many megapixels?

Betty try www.aquameds.com The medication I'm using is for Tape Worms.