Actually, cavalry units were still issued swords into WWII, some even carried lances. English, Poles, Russians, and the Japanese rode with swords into battle, along with their rifles.
What I was commenting about is infantry use of swords, particularly instances when entire units fought a battle with swords. -I'm not talking about officers or individual soldiers wielding a sword here or there.
If you want to talk about obscure use of weapons, the last casualty caused by a longbow was in WWII when an English officer nailed a German soldier with his longbow during a rearguard action at Dunkirk. -This doesn't mean that longbows were used in WWII.