As "little guys" go, I can't think of anyone as tough as Deividas Taurosevicius (or "DT", as I prefer to call him). I was there for his first MMA bout, when he was just an ex-rugby player fresh off the boat from Lithuania, repping some karate school as he took on Yamasaki's Muay Thai instructor Mike Acosta at the very first Sportfighting event. The dude ate everything Acosta threw at him, including a hellacious spinning backfist, and though DT's effort was a losing one, he just would not quit. Some intense jiu-jitsu study after that and the man was suddenly a beast.
The only other loss DT had in the Northeast circuit was against Frankie Edgar, which put him as one of the top three lightweights in the area (Edgar and Jim Miller made up the rest of the trio). Then he was kicking ass in the IFL, and after that, the WEC. His losses came at the hands of Ryan Schultz, LC Davis and Wilson Reis (in Bellator), and it was always via decision - sometimes even just a razor-close one.
His English, while not always the best, has vastly improved over the years. But he's always been the nicest, friendliest of dudes, and he's lost none of that toughness. Case in point: his ROC 38 bout against Edson Barboza's training partner, Marlon Moraes.
Moraes came out and was outstriking DT on the feet something fierce (of course, what would you expect from the guy who has to spar with Barboza?). DT struggled to get things to the ground, but the Brazilian was instantly on his back, working for a choke. Then, the most amazing thing happened, as DT escaped, trapped Moraes' arm in a head/arm choke, squeezed, and tapped the fucker out. It was such a rapid and stunning turn of events that Dave Tirelli, who was judging, turned to me and we both exclaimed "Wow!" The bout was all of two and a half minutes.
DT runs a school out on Long Island, so when he's ready to hang up the gloves and retire his ROC featherweight championship belt, he's got something to keep him busy. But when he does finally call it quits, I doubt the scene will ever see any else tougher. If I had never seen the cuts and abrasions he's suffered in his fights up close with my own eyes, I'd swear the man was bullet-proof. Although I doubt even shooting him would stop him.