HMS Hood, HMS Illustrious, King George V battleship, any other BB but those are all very rare and unlikely you'll sink them all in one patrol, If you do manage to accomplish such a feat you will have torpedoed England straight out of the war
But for somewhat less challenging methods, I'd stick with the Large Merchants and Large Cargos they're fairly common and 10.000 tons or slightly more each, tankers are also good, though harder to sink IMO.
Personally I've never managed to get to 100k simply because I'm not the patient type so I tend to miss more often