Thing_Stop

This stops the specified actor's current movement by setting its acceleration and speed to 0.

This example freezes the player and prints a message to the player, as well as freezing him in place.

Script 1 (VOID)
{
        Print(s:"STOP RIGHT THERE YOU FREAK!");

        Thing_Stop(0);
        SetPlayerProperty(0, 1, PROP_TOTALLYFROZEN);
}