They’re not predefined in C#. They’re defined by the framework.
The Action and Func delegate families are wider than you’ve shown – they go up to
Action<T1, T2, T3, T4>
and
Func<T1, T2, T3, T4, TResult>
Another common-ish one in .NET 2.0 for list manipulation (before LINQ) is Predicate<T>.
For working with threads:
ThreadStart
ParameterizedThreadStart
WaitCallback
TimerCallback
AsyncCallback