Gregg Sciabica, known across trading forums simply as "Lx21," is one of the most successful and most private penny-stock day traders in the game. He came to markets sideways: in 1999 he started a contracting business building custom swing sets, and after a year of hard work cleared about $25,000 in profit. Looking to grow that money during his company's offseason, he moved it into the stock market, and by the end of his first year of trading the account had grown to roughly $700,000.

From there Sciabica kept compounding, eventually surpassing $10 million in tracked profits on Profit.ly, putting him in the same rarefied tier as Tim Grittani. His edge is a self-built system: he studied other traders but deliberately refused to lean on anyone else's playbook, building a method he could sustain on his own. A longtime member of Investors Underground, he keeps an unusually low public profile for someone with his record, rarely giving interviews and letting the audited numbers speak.