You're in luck, cause Italy did take a crack at producing effective weapons in the war against the Allies and did have some damn good stuff to show off. Problem was that due to Italy's poor industrial base compared to manufacturing titans like the US and USSR, what weapons they could make were never produced in the numbers needed to make much of a dent in the war effort as a whole.

First up is the manned torpedo, a concept tested by the British at first, but saw its first practical and effective use by the Italians in WWII. This submersible carried a magnetic mine as a warhead at the front and was piloted by 2 scuba divers to sneak into enemy harbors while their ships were at port. The divers would take out and attach the mine onto the hull of enemy ships docked at port and detonate.

The most effective use of this weapon took place in Alexandria harbor on December 19, 1941 where 3 manned torpedoes successfully disabled the British battleships HMS Queen Elizabeth and HMS Valiant, as well as damaging 1 destroyer and 1 tanker. In just one night operation, the Italian navy gained temporary naval superiority over the British in the Eastern Mediterranean. The operation was so effective that the British made it a point to forbid Italy from possessing or experimenting with any manned torpedoes in the final peace treaty after WWII.

When it comes to Italy's air force, they were able to produce 2 high quality planes that earned respect among both allied and German pilots. The C.202 Folgore and the G.55 Centauro were fantastic fighter aircraft that were often able to outmaneuver their Allied contemporaries such as the Spitfire, P-51 Mustang, and the P-38 Lightning. While the Folgore and Centaro were deadly dogfighters, the numbers Italy could manufacture and field were nowhere near the numbers necessary to command air superiority for prolonged periods of time. With only 1,100 Folgores and only a mere 300 Centaro's made (Compare that with the German Bf 109, with nearly 35,000 produced), any advantage Italian fighters had was negated by the sheer numbers of Allied craft that could be fielded against them.

When it comes to the Army though, quality and reliability of their weapons were on the whole lacking, one bright spot though was in Italy's main submachine gun. In an army of outdated and unreliable infantry weapons, the Baretta Model 38 stood out as one of the best submachine guns of the war, highly praised by both German and Allied armies as being robust, reliable, and accurate at surprising ranges compared to contemporaries such as the Thompson and Sten Gun. The Model 38 went far as to be the preferred choice of German SS and Fallschirmjäger when it came to submachine guns, with American and British units also using captured guns in their own army, with most units citing the quality of the parts and the gun's reliability as its strongest points.

If you want to read more, check out Italian Small Arms of the First and Second World Wars by Ralph Riccio, Courage Alone: The Italian Air Force 1940-1943 by Chris Dunning, and The Italian Navy in World War II by James Sadkovich (though I only touched one one weapon in the Italian Navy's arsenal, Italy's Navy as a whole was by far the best equipped and sufficiently battle ready at the start of the war, kneecapped by lack of oil which doomed their rather impressive Navy to sitting in port for most of the war, and reading Sadkovich's book gives a much better assessment of Italy's Navy as a whole rather than just an effective arm of it as I listed)