Were there any WWII era guns designed for close range combat?

As you are likely aware, the large calibre rifles fielded by the various armies, such as the M1, K98k, or M91/30, had very long effective ranges, far beyond what the average engagement was being fought at. Based on the experiences of World War II, this helped to fuel the development of the 'intermediate cartridge' such as the 5.56x45 and 7.62x39. It was by no means solely a post-war development though, and really, despite the narrative, it isn't wrong to say that there was movement in the direction of reduction of size before the war even happened.

First, as regards rifles, there is the rise of shorter carbines, best exemplified by the M44 Mosin rifle. Its development actually predates the war, but its earlier M38 version was designed mainly with second-line units, such as artillerymen, as well as cavalry, in mind, and the longer 91/30 was the primary arm when war broke out. Practical experience though proved the M91/30 was ungainly, and the very strong demand for a smaller issue weapon saw the M44, an improvement on the earlier M38 design, became the primary production version of the Mosin and M91/30 production was scaled down. Over 6,000,000 M44 carbines were made in 1944 and 1945. Other countries also developed carbine weapons, such as the M1 Carbine of the US military and the "Jungle Carbine" version of the Lee-Enfield with the British, but they were not slated for whole scale replacement of the existing long rifles.

Now, as for the second major group we have submachine guns. These predated World War II, with their development history coming from the First World War, but aside from a very small handful, such as the limited number of M18s issued by Germany, the SMG had its coming of age in World War II. Most major powers had their own design, such as the American 'Tommy Gun', British Sten, Soviet PPSh and PPS, or German MP40 - only the Japanese didn't produce one in significant numbers - and there were a number of examples from smaller nations too such as the Australian Owen Gun and the Finnish 'Suomi'. Submachine guns are capable of automatic fire, and shoot a pistol round, which makes them very well suited for close-quarters combat. Especially in urban combat like Stalingrad, SMGs were considered essential weapons.

Cited Lapins mosin book.