Volatile Gelatin

It lobs a blob at the closest enemy every couple of seconds, provided nothing is blocking the view between you. The shot arcs, so it drops as it travels, and it will skip off walls once or twice before dying. The damage is classless and fixed, meaning no armor set, buff or prefix will ever raise it by a single point.

By the time you own this the damage is small, but the shove on each hit is heavy. Something walking at you gets pushed back repeatedly, which buys room in a cramped fight. The catch is that most Expert hardmode enemies resist knockback well enough that this stops mattering quickly.

Queen Slime tends to die after you already have accessories that add a real percentage to your own weapons, and those win a slot every time. The honest use is passive: keep it on during fishing trips, ore runs and long builds, where anything firing for free beats an empty slot. Swap it out before a boss.