National Ballpoint Pen Day (10 June)

Yes, on this day in 1943, László and György Bíró got the US patent for their amazing new device. They were refugees from Hungary via Argentina.
I prefer pencils (see 30 March). But I might celebrate ballpoint day by burning a few. Once you get them lit, they drip gobs of burning plastic and give off toxic smoke. Very festive.
There's a chapter on Biro in Philip Dodd's book _The Reverend Guppy's Aquarium_, which I enjoyed more than I expected. It also covers eponymous folks like Jules Léotard, Adolphe Sax and Roy Jacuzzi. Really gives you an idea of how much work is involved in perfecting an invention which gets your name into the dictionary.