Other then Prien who do you like for U-boat skippers. Years ago I read a book Titled "Grey Wolves, Grey Seas" about U-124 and Johann 'Jochen' Mohr.

   Mohr was one of the few U-boat officers to spend his entire career with the same boat. (U-124) Mohr did his first three patrols under the command of Georg Wilhelm Schulz, (Knights Cross 4 April 1941)

    Mohr took command of U-124 on 8 Sept. 1941. On his first patrol in November 1941 Mohr sank the light cruiser HMS Dunedin, and in 1942 the French cruiser Mimosa.

    Mohr had great success off the east coast of the United States as shown by this little diddy he composed on his way back from patrol in American waters;

                          The moon night is black as ink

                          Off Hatteras the tankers sink

                          While sadly Roosevelt counts the score

                           Some fifty thousand ton

                            By Mohr

      Mohr was at sea when he was awarded the Knights Cross on 27 March 1942. So his crew made him one that he wore until he got back to port. It's said he liked the RK made by his men more then the one awarded to him by Donitz.

       On 13 January 1943 Mohr was awarded the Oak Leaves to his Knights Cross.

       Johann Mohr was killed on 2 April 1943 when his boat was sunk off Portugal by the British corvette HMS Stonecrop and the sloop HMS Black Swan.

Korvettenkapitaen Adalbert Schnee, twelve patrols, 21 vessels taken out (90,847 tons GRT), two auxilary warships (5700 GRT) and damage to three other vessels (Totalling 28,820 GRT). He was awarded the Oakleaves to his RK after his seventh patrol in U-201, during this patrol he sank over 41,000 GRT of shipping.

And then there's the instance in which, when commanding U-2511 (A Type XXI boat) he was to patrol the Carribean, but he recieved the Cease Fire order that signalled Germany's surrender in 1945. He was on his way back when he noticed a taskforce including the cruiser HMS Norfolk, which he began a dummy attack on. He approached to within 500 metres of HMS Norfolk, undetected, and then having proved a point to both himself and his crew, he returned to base.

After the war he had an opportunity to talk with the officers and crew of HMS Norfolk, who were amazed he got within 500 metres.

All of this from Chris Bishop's book "Kriegsmarine U-Boats, 1939-45." I'd highly recommend it, probably one of the single best books for U-Boats you can possibly find.