Another thread prompted this. Only breakdowns that have required the indignity of towing home/garage, or that have caused the vehicle to stop, and not restart for ages.
Here's mine.
My own cars:
Acclaim - lost all power (racing another car

). Dried out with Fospro, restarted 15m later
Belmont - pistons and valves had a chit-chat due to Vauxhall's shitty gearboxes. New engine needed. Mate towed home.
Astra GTE - Fuel Pump relay failure. New relay.
Rover 216 - Ignitor unit. A spare fell off the production line into her pocket a few days later

Nova 1.2 - Brake caliper seized. Several buckets of water required every mile

Rover 25 - Fuel pump failure, replaced under warranty.
MV6 - crank sensor, outside Dijon, France. Car came home a few days after me

TB1 - waterpump seal. Limped home as I luckily water carrying water and oil.
TB2 - Knocked the sump plug off at speed

. MV6 towed it home.
Golden Nugget - "Something broke" after a high speed run, let go at an ABS meet. Indignity of using Tunnie's Towing Services
TBE - "TBA"
Cars that weren't mine, but I was responsible for.
Dad's Escort - hit signpost and tree. Drove home, got a thick ear

Ital van - wheel overtook me under heavy braking for a bend. Tow truck back to garage.
Ital van (different one) - engine fell out when going flat out. Towed back to garage.
Escort van - hit a lamppost, drove back to garage. Only left garage 15m earlier, after being towed in earlier for running out of fuel

Escort van - hit a Capri. Drove back to garage.
Escort van - hit a tree. Drove back to garage.
Transit - oil filter fell off. Only been serviced 2 miles before. Tow truck.
Transit - fuel filter came undone. Only been serviced 12 miles (and 15 gallons!) before. Towtruck.