The reviews I read before I got the game said that, once you'd upgraded your proton blaster completely, it was the best weapon in the game and you wouldn't need any of the other weapons. I'm only half of the way through the game, but I have to say that I'm finding the blue shock wave blaster to be the best weapon so far. The slime shooter is pretty cool, but the stasis stream and the shock wave "shotgun"-type weapon are my favorites.

When he was stationary, I used the Meson Collider on him. However, the proton steam was exceptionally effective because of its accuracy and ability to change direction mid-shot.