For example, the unity function Vector3.Smoothdamp modifies "currentVelocity"
The function signature is (from Unity scripting manual):
static function SmoothDamp (current : Vector3, target : Vector3, ref currentVelocity : Vector3, smoothTime : float, maxSpeed : float = Mathf.Infinity, deltaTime : float = Time.deltaTime) : Vector3
The function uses the "ref" keyword to (apparently) indicate what looks like C-style indirection (i.e., *currentVelocity). The "ref" keyword is also a feature of C# (as well as "out"), which produces the same effect in C#.
answered Feb 07 '12 at 09:26 PM