ORCA (Optimal Reciprocal Collision Avoidance)
RVO's successor: cast avoidance as a linear program and pick the allowed velocity closest to the one you actually wanted.
Van den Berg, Guy, Lin and Manocha showed in 2011 that "don't collide with this neighbour for the next half-second" can be written as a half-plane of permitted velocities per neighbour. The intersection of all those half-planes is the set of provably safe velocities, and the agent picks the point in it closest to its preferred velocity — a small linear program per agent per frame.
Unlike RVO, ORCA gives a formal guarantee of collision-free motion within the time window and scales to thousands of agents. Its reference library, RVO2, made it the default choice for crowds in games and robotics.