Shooting Curve Flatteners
Randomly choosing an angle in the reachable area is a good fallback strategy. DrussGT does this, although this gun rarely gets used. It is more as a safety in case someone copy-pastes his gun and then surfs it.
People have experimented a lot with Anti-Surfer guns over the years, but nothing seems to work better than a GF gun that only works on very recent data. And once the enemy starts flattening there is very little you can do. At this point fighting at a distance or bulletpower where you are more competitive might be a better idea, and turn on your own curve flattening as well.