For openers, a closer

When he finally hangs up his spikes, Jonathan Papelbon should consider becoming a rock star. The Sox closer was at a party celebrating the opening of the Back Bay bar McGreevy's and impressed us with his guitar skills. Unbowed by his blown save earlier in the day, Papelbon challenged Dropkick Murphy Ken Casey to a game of Guitar Hero in the bar's VIP room and actually won. (The pair squared off on "Story of My Life" by Social Distortion.) "I haven't played a video game since Donkey Kong," said Casey, a partner in McGreevy's with former 3rd Bass MC Peter Nash. Others making an appearance at Sunday's post-game party included: Sox pitcher Clay Buchholz; Celtic Scot Pollard; Bruins Shawn Thornton and Jeremy Reich; NESN's Andy Brickley and Heidi Watney; Billy Bulger and Senator Jack Hart; movie producers Kris Meyer and Keith Dorrington, who's working with Mark Wahlberg on "The Fighter"; Fenway Recordings owner Mark Kates; Ben Mezrich's wife, Tonya Chen; former NHL ref Paul Stewart; and Celts publicist Heather Walker, who told us she's about to take a well-deserved vacation. Better than the beer at McGreevy's are the baseball artifacts that line the walls of the Boylston Street bar. "It's more of a sports museum with TVs and a bar than the other way around," said Casey.

Message on a sweet spot

A bat signed by Babe Ruth would be valuable. But a bat inscribed to a Broadway starlet whose husband produced "No, No, Nanette"? That could be worth big bucks. We'll find out when Hunt Auctions sells the stick next month in New York. "There's no more Curse of the Bambino, and Yankee Stadium is coming down," Lon Clark, the bat's current owner, told us yesterday. "Now seems like the right time to sell it." In 1920, Sox owner Harry Frazee famously sold Ruth's contract to the Yankees and invested the money in the Broadway musical "No, No, Nanette." The Yanks went on to win 26 World Series titles while the BoSox were bereft. The bat, which some think could fetch up to $200,000, was signed by the Babe on April 27, 1924: "To Tessa Kosta, From Babe Ruth." Kosta's husband was Richard Madden, one of the "Nanette" producers. Clark said he wouldn't mind if someone from Boston is the high bidder. "Boston has as much right to the Babe as anyone," he said. "Maybe more."

Howdy there, Rex

Jay Leno invited his childhood hero Rex Trailer to be his guest at the late-night talk show host's gig in Lowell over the weekend. The TV cowboy, who'll turn 80 this year, even got on stage and led the sold-out crowd in a rendition of the "Boomtown" theme song, and received a standing ovation. Leno's show was a fund-raiser for Middlesex Community College. . . . Natasha Bedingfield hosted a private party last night at the Boston Billiard Club. The British songbird plays tonight at the Paradise.

Gisele Bundchen spent the weekend in her native Brazil, where she walked the runway for Colcci. Offstage, we're told, she spent much of her time in the arms of another man. No, Gi's not stepping out on Pats QB Tom Brady. Bundchen was with Rodrigo Hilbert, the Brazilian beefcake with whom she's shooting Colcci's new summer campaign. As always happens when the world's richest supermodel returns home, Bundchen was pestered by paparazzi, fans, and reporters, one of whom asked why she's never dated a Brazilian man. "I love Brazilian men," Bundchen replied with a wink. "You're all good."

A rep for Nestle - one of the sponsors of this weekend's Nantucket Film Fest - was none too happy to see Irena Salina's documentary "Flow: For the Love of Water." How could we tell? He stomped out of the screening. The film, which includes the work of Vineyard-based author William E. Marks, depicts bottled water as a scam. Word is Salina's received veiled death threats for exposing the threat posed by water privatization, and that doesn't necessarily upset the moviemakers. Said coproducer Gill Holland: "We hope they'll come after us - we'll get lots of good press."

During his chat with Time magazine's Richard Corliss at the Nantucket Film Festival, William H. Macy recalled founding the late "off-Loop" Nicholas Theatre in Chicago with David Mamet. They bought seats from a junkyard with a check that bounced "higher than a kite," and then proceeded to sell naming rights to donors - twice. In his new film, a movie-biz sendup called "The Deal," Macy plays a scruffy screenwriter romancing a character played by Meg Ryan. Macy and director Steve Schachter raised the dough for the film on the cocktail-party circuit. "We warned investors, 'You could lose every dime - you could also buy a jet.' " Quoting his mentor Mamet, Macy advised the audience: "Always tell the truth. It's the easiest thing to remember."

Ben Affleck's travels to the Congo region of Africa will be the subject of Thursday's "Nightline." The actor, who's been to Africa three times in the past eight months, was joined this time by "Nightline" producer Max Culhane and photographer Doug Vogt. They recorded Affleck as he made his way through refugee camps and hospitals, and met with warlords, relief workers, and members of parliament. Says the actor: "What's going on here in this country is humanitarian disaster. I think just helping people understand that could have a real ripple effect down the road and this piece will be one small step in that."

'I plan to deliver some great material this year.' LL Cool J, talking to Billboard about his new album, "Exit 13," out Aug. 5.

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