Name is Dangerously Close To Mark "Buffalo"
Seems like he dodged a major bullet with his last name. There has never been a famous Hollywood bigshot with the surname of "Buffalo"
Mark Buffalo sounds like a fictional character's name. His range and his style of acting would not benefit from being named Mark Buffalo, he would have had to take on a stage name and that would have taken a bit of extra effort on his part
On the flip side, if he made it big he could have easily gone into the booming buffalo wing business and somehow parlayed his name into either a sponsorship deal or the creation of his own wing sauce. Ultimately we will never know what could have been if his last name had differed by a single letter