Outside of Descent... the Portal gun (it counts, right?).
When it comes to descent, I love the D1/D2 plasma cannon. A little less damage than laser level 4 quad, but it keeps things stunned for ages.
(all damages per bolt. Quad lasers fire two "dead" bolts while the two others do 1.5x damage)Laser level 4 damage: 13. This is base.Quad Laser level 4 damage: 19.5.Plasma Damage: 11ROFs are expressed as the amount of seconds before you can fire the next shot. Laser ROF: 0.20 sec (rounded due to fixed imprecision)Plasma ROF: 0.15 secLaser dmg per sec: 19.5 (base damage) * 5 (shots per sec) * 2 (two projectiles) = 195 dmg (lots)Plasma dmg per sec: 11 * 6.66 * 2 = ~146.52