The Lindblum probably takes the cake. Sure, it's enormous and probably inefficient as all get out, but it looks absolutely amazing.
Exalted's Titan Citidals probably count as well. Essentially a nigh-invulnerable floating city with more plasma canons and fighter bays than is really needed. And, because this is Exalted, it can unfold into a miles-wide lens that can fire a laser so grossly overpowered that anything caught in its mile-diameter is destroyed unless it is 100% invincible. The Eye of Judgement literally does infinite damage, and survivors can only weather that with a perfect defense (defense trumping offense in Exalted). In that vein is also the Five Metal Shrike, a ship with most of that firepower but much, much smaller and more efficient (not so many energy canons, but it's shielding is perfect when active and its main gun, the Godspear of All Searing Noon, is as disruptive as the Eye of Judgement, merely more precise.