@TheHealingDoctor i have a couple suggestions. First of all, a 6 wide, 10 long supercannon that has no fire, a lot of penetration that can penetrate thru 10 layers of corridors and then break a reactor and a little damage and has the same fire rate as the standard cannon. The cannnon is blue and the the bullet is as big as the rockets but they look like the big cannon's bullet.
My second suggestion is a 1 wide 2 long gun that shoots faster than a point defence system but has 0 penetration and less damage than the laser.
Third suggestion: a pulse ion cannon which looks like the standard cannon that shoots ion pulses which do as much damage as an ion beam but has a higher fire rate and use less energy than the normal ion beam.
Fourth suggestion: a shield buster which 2-shots a shield and does no damage to anything else.
Fifth suggestion: corner standard cannon, corner big cannon, corner triple cannon, corner quintuple cannon, corner everything.
Sixth suggesion: RC-cannon which is basicly a rocket launcher but when its near the enemy ship it explodes into 5 bullets which does as much damage as a laser.
Seventh suggestion: Bouncing cannon which when it hits an enemy ship, 2 small bullets which does 1/3 of the original's bullet damage bounce out of where the original's bullet hit to hit some place else.
Eight suggestion: a bullet that shoots anywhere but than change its direction towards the targeted place. A bit like rockets.
Ninth suggestion: a heat cannon which penetrates thru 4 blocks and sets fire to everything it touches.
Tenth suggestion: a recoil cannon which when it hits the enemy ship, it pushes the enemy ship away. Also a big recoil cannon which pushes the enemy further, does more damage but also gives yourself a bit of recoil.
(it took me 2 hours and 23 minutes to get every idea and write them here.)