There is "The Machine That Goes Ping!!", although as it was stuck on as an additional (and therefore minimised) cost, it is certainly NOT the most expensive machine in the hospital, sorry - ship!
Like the T42 sonar, the T45 sonar has what can be best described as "Oh ****!" range when it comes to submarines (i think the official term is 'limited capability'). It's really meant to help it avoid mines. It's a trade off between the the ships primary AAW mission, a residual ASW capacity (which hasn't stopped the French and Italians putting a half way decent sonar in their Horizon class frigates - cousins of the T45) and of course cost. It's primary organic ASW asset of course is it's helo.