Paper would be my candidate. Being able to store huge amounts of information in thousands of books in a room transformed human societies much more than antibiotics did.

How the humans invented something so incredibly useful? Most probably after watching "useless" social wasps to mash bark to make its nests.

A few that spring to mind, all plant blazed:

Aspirin occurs naturally in Willow bark; morphine and codeine from opium poppies; ephedrine and amphetamine is derived from Ephedra sinica (Ma Huang); quinine and it's derivatives from Cinchona calisaya; digoxin from foxglove (Digitalis lanata).

And botox from the bacterium Clostridium botulinum and related species has medical uses primarily for muscle spasticity conditions and migraines.

Salicin occurs naturally in willow, not aspirin. It's a prodrug of salicylic acid, which has some anti-inflammatory effects.

Aspirin is acetylsalicylic acid. It's also a prodrug of salicylic acid, but it has additional anti-inflammatory and anti-thrombotic effects, because unlike salicylic acid itself, it can irreversibly inactivate COX enzymes (enzymes that synthesize compounds needed for inflammation and blood clotting) by acetylating them. It's also less irritating to the digestive system.

crop disease resistance maybe? i sure do like eating.