Mr Warren Buffett would be an easy choice after he was mentored by Benjamin Graham.  However, the major change came with he met Mr Charlie Munger who advised him to hold the stocks "forever". 

James Harris Simons (better known as Jim Simons) is an American billionaire, award-winning mathematician and hedge fund manager who founded Renaissance Technologies in 1982. As of the end of 2020, the New York-based hedge fund has over $165 billion worth of discretionary assets under management and over $92 billion in managed 13F securities.  Some regarded him as the greatest who incorporated the use of quantitative analysis into his investment strategy.

Personally Peter Lynch would be my favourite as he amassed a massive portfolio of over 1400 stocks at one time. 

From Forbes:
Peter Lynch gained his fame as the portfolio manager of the Fidelity Magellan mutual fund, which he took control of in 1977. During his 13-year tenure as portfolio manager, he grew its asset base from $20 million to $14 billion and beat the S&P 500 in 11 out of 13 years, with a 29.2% average annual rate of return.

He is also a great educator and has provided great humor, wisdom and wit in his interviews.