My guess is the Crank Position Sensor. This vital part is the conductor of
the orchestra, and if it fails then the computer won't know where the engine
is, and it won't fire the injectors or set off the ignition spark  On some
systems, the fuel pump will even be shut down - the theory being that if the
ignition isn't going to be taking place, there is no point in delivering
fuel.

Some systems use a Cam Position Sensor, but I think this does the same job
as the Crank Sensor, it just does it in a different place.