I wouldn’t call any extinction event a favorite, because it is a loss. An interesting one that is less known than the Dodo is that the wake island rail bird was hunted to extinction by starving Japanese soldiers in WWII. The Americans blockaded the island, trapping the Japanese there, and they ate all the birds in just a couple years time.

I think it’s an interesting extinction because it’s an unintended casualty of war.

The oxygenation of the ocean. Never knew that was a mass extinction! So much interesting stuff came from that!

The Holocene.

Discussion: you can have an “extinction event” in any ecosystem-- not just biological ones.

For example, the abandonment of steam locomotives in the mid-20th-century, or the Home Computer crash of the 1980s.

Similar to a biological mass extinction, you have:

• A discernable ecosystem change, either a sudden event (the introduction of reliable, mass-produced diesel locomotives), or a measurable decline of “habitability factors” (as hundreds of firms brought cheap 8-bit computers to market, retail space and overall consumer interest saturated)
• a rapid diversification of new and exotic types to fill the vacated niches (the cabless “B-unit” and flexible “road-switcher” locomotive types didn’t exist in the steam era. The post-crash computer market brought in new entrants like cheap IBM clones, the C128 and Atari 130XE, all chasing a sub-$1000 market that was now free of Sinclair, Coleco, and Texas Instruments)
• followed by a shake out and consolidation of the survivors/winners as they select for fitness in the new world (ALCO was a strong #2 in the diesel locomotive market in 1950, but didn’t make it to 1970. The C128 never became the world-beater its predecessor did.)
• a few niches largely untouched (China was still building steam locomotives into the 1990s. The Apple II series lasted about as long.)

The one with the internet, whatever that’s called.