The mildest OC's, as mentioned, are the Merkur 1904's and similar (Goodfellas, etc). They didn't work for me.
Another OC which is relatively mild but shaves VERY nicely is my Gillette New short comb. Long comb is slightly more aggressive for me but also excellent. This may change as I am still trying out the short comb.
BOTOC, GNU, LEMS, SERLover, Stirling Syndicate
New Shaver Guide - http://badgerandblade.com/vb/showthread.php/373872-My-short-and-somewhat-misleading-shaving-guide-for-those-foolish-enough-to-listen