got my S-Rank tonight, a Sword ( Go me! ), the stats are really crappy but I'm guessing it gets powered up when you use it with other S-Ranks... dunno....
but I've read at POSW and Ragol.com that using an S-Rank will get you banned online, if you repeat a challenge after getting srank you'll get the two shields you get offline (for ARank and BRank) no Rings!
P.S. It is highly suggested for everyone not to get your S-Rank yet until this is resolved.