Insofar as 'ridiculous but amusing' weapons, I would want a weapon that is essentially a melee weapon at heart. A long pole with two overhand grips, a powerful motor beneath the handholds (for weight distribution) and drive shaft in the middle, and at the far end, a wide magnetically charged disc, with about a meter's worth of monofilament wire with a magnet endcap on the end. You turn this on, the main drive starts spinning, and the monofilament wire starts whirling about, the magnetic shielding of the disc keeping the wire away from you by electromagnetically messing with the end cap on that wire. You can swing it around and basically start shearing irregularly-shaped chunks out of most things, and if you left it pointed in one area would eventually get a dome-shaped clear space about two meters in diameter and a lot of oddly shaped bits of debris on the floor around you (wall based, screamy, or otherwise). An effect not unlike Hell's weed-whacker.