Rav Yaakov Yisrael Kanievsky (1899 – August 10, 1985), best known as the Steipler Gaon, spent most of his life shunning the limelight, despite being the unofficial successor of his brother-in-law, the Chazon Ish, upon his petira in 1953. His life was spent learning Torah and in uncompromising meticulousness in keeping every mitzvah.
Though he held no official position, the Steipler was universally recognized and was consulted by individuals from all walks of life on every imaginable problem and many claimed that he displayed knowledge which was inconceivable by natural means. In his relation with people he seemed both tough and tender, but as one who knew him very intimately said, "he would give someone a slap in order to sweeten the judgment."
You may be interested in this picture of the Steipler Gaon:
The Steipler Gaon's biography is available from Artscroll.