Pillboxing is admittedly a cheap tactic, but it works. Although only medium to long range ships with a high fire rate should try it, it usually works against short range opponents.
Pillboxing is a very simple tactic - once in battle, a moving ship can hit a planet, be a victim of the relativity effect, medium to high acceleration ships like the Yehat Terminator can use a gravity whip to surprise you by tearing you apart flying at high speeds - overall, moving is dangerous.
To avoid all this, you just do not move, and shoot when the enemy is near. When your ship is a safe distance from a planet, you cannot be surprised. The Utwig Jugger is a great example of a pillbox ship. A small and light ship like the Pkunk Fury must surprise the player so he can get close enough to damage the ship. The Jugger doesn't have to care about his battery ending, so he can sit there and wait till the obviously annoyed Pkunk tries to fly in range. This ends 95% of the time with the suicidal death of the Pkunk. A fine addition for any "pillboxer" would also be a shielding capacity like that of the Terminator or the Jugger.