Ford Focus Mk1, 2001, 1.6 Petrol
Whilst on holiday a couple of weeks back the speedometer became erratic and then stopped working. No problem I thought - it had happened before and at that time I did around 400 miles before replacing the speedometer sensor. My Sat Nav was used as the speed indicator.
A hour of driving later, and just turning off a main road into a country lane, the engine cut out completely with a slight smell of (electrical) burning.
As it was getting dark and raining the car was recovered to a local garage 5 minutes walk from where I was staying. The next day being a Sunday, and the garage being closed, I decided to take a look at what may be wrong. The 20A "engine" fuse had blown and on swapping it with another fuse in the box I could start the car again BUT with a extremely large amount of white 'electrical smoke'.
In the end I was in luck in that the fault turned out to be only the speedometer sensor which had caught fire and melted. A new sensor, a fuse and a total bill for just over £100 from the local garage got the fault sorted and the car has done 500+ miles since without problems.
On my car the speedo sensor seem to last 70K miles and if it it happens again I will definitely disconnect the wires to it the first sign of the same problem. However, I don't think I will have the car the next time it is due for failure :)