In Dragonball Z, when do the characters start moving faster than light if at all?
DBZ is full of weak characters moving insanely fast.
Eg: Raditz vs Goku and Piccolo - first fight:
Other than that, as Ben mentioned:
Instant Transmission technique
From the wiki, the "Instant Transmition" is the only one that comes to mind when exceeding the speed of light:
The FUNimation dub states that this technique allows the user to travel at the speed of light, this is not possible, as Goku has been seen using it to travel to other planets and even galaxies in a literal instant. Given that the distances from other solar systems would take light entire years to travel across, this would not be possible.
While the excerpt states that "this is not possible", I believe it is stating that their speeds exceed the speed of light.