(FORTUNE Magazine) – Joel J. Cohen Cohen, 47, is known as Mr. Billion these days in the corridors of the New York law firm Davis Polk & Wardwell, where he has been a partner since 1969. In one memorable June weekend, Cohen shepherded to a close the two largest mergers ever seen this side of the petroleum industry: General Motors' $5-billion pickup of Hughes Aircraft and R.J. Reynolds's $4.9-billion buy of Nabisco Brands. Cohen believes the recent spate of megadeals resulted mainly from the influence of attractive stock values, sinking interest rates, and T. Boone Pickens. Another factor: the federal government's ''fairly accommodating'' antitrust posture. Michael Silverstein Five years ago Silverstein, 30, was just another of the good old Good Olds Guys in the Bronx, half owner of an Oldsmobile dealership with his father. He has since found the right bandwagon to hop on, and today his Crest Auto Leasing is probably the largest privately owned leaser of cars to individuals in the U.S., turning over $100 million of expensive autos a year. Silverstein sells the leases to banks and the credit corporations of large companies, such < as General Electric, which get an investment tax credit, and in return he gets an enticing monthly rate for his customers. Silverstein has 12 offices in metropolitan New York and plans to move into Hartford and Boston soon, then south to Maryland next year. Kay Koplovitz Though by all accounts an upstanding citizen, Koplovitz, 40, would like to see everybody wired. Her wish stems from her position as chief executive of the USA Network, the highest-rated advertiser-supported network on cable TV. Formerly an editor, publisher, and TV producer, Koplovitz has moved the channel (which is one-third owned by Time Inc., publisher of FORTUNE) away from its original reliance on sports to a more general format that includes game shows and sitcoms. For the fall Koplovitz promises the return of Dick Cavett in a weekly entertainment show and the reincarnation of Don Adams, a.k.a. Secret Agent Maxwell Smart, this time as -- would you believe, a grocery store manager? Harold J. Pareti When Pareti, 37, was president of People Express, he learned that routes to out-of-the-way places from an underused airport could bring in a lot of money, and that giving his employees several jobs apiece could save a lot. Pareti will use both stratagems when he starts his own airline this fall. But unlike his alma mater, Presidential Airways will have frills to lure the business traveler, including free meals, advance ticketing, and a first-class section. Pareti plans to start flying in October from his hub at Dulles Airport, 25 miles from Washington, to cities in New England, the Ohio Valley, and Florida for about 60% less than current coach prices. To forestall an early undercapitalized demise, he has filed for a $15-million public stock offering, raised $14 million in equity privately, and lined up enough financing to pay for ten refurbished Boeing 737s. Henry Semmelhack Though it isn't likely that the word silicon will soon be appended to any valley, prairie, or other natural habitat near Buffalo, New York, Semmelhack, 48, has established a high-tech foothold there. While nearly all law firms have word-processing equipment, his Barrister Information Systems sells lawyers a hardware and software package that includes database management and accounting functions tailored to legal needs. Barrister has grown 30% a year since Semmelhack spun it off from his first company, a defense contractor, in 1982. Following sales of $21 million last fiscal year and earnings that topped $1 million, Barrister went public in July. Semmelhack also trains law offices to use his gear. ''Service is very important,'' he says. ''A lawyer has very little tolerance for technology.''