What Second World War technology might still be useful

What Second World War technology would be worth resurrecting for another fifty years?

Most technology is obsolete, but modernized heavy torpedoes could still offer a powerful long-range anti-submarine option.

Heavy Second World War torpedo designs could be reconsidered with modern engines and sonar for long-range anti-submarine use. That would require substantial modernization of the old weapons. The attraction is the ability to inflict enough damage with a small number of hits. Armour belts receive a brief favourable mention, but most wartime technology has moved on.