BOSTON - He was a prolific producer of rebounds and record albums. And nicknames, too, as if at 7-foot-1 and 350 pounds he was too big for the simple "Shaq" that made him an instantly recognizable, one-name star in all of his endeavors.

Shaquille O'Neal had more than 28,000 points and almost 4 million Twitter followers. He appeared in six NBA finals, three times as the MVP, and seven feature films, twice in a starring role.

A 15-time All-Star, four-time champion and the 2000 NBA Most Valuable Player, the 39-year-old O'Neal announced his retirement on Twitter on Wednesday after spending most of his 19th season on the Boston Celtics bench, in street clothes because of leg injuries.

Along with a mid-afternoon tweet saying, "im retiring," O'Neal included a link to a 16-second video of him saying, "We did it; 19 years, baby. Thank you very much. That's why I'm telling you first: I'm about to retire. Love you. Talk to you soon."

An inveterate prankster who gave himself a new nickname - or several - in each of his six NBA cities, O'Neal did not notify his latest team, leaving it wondering about his plans. He played just 37 games this season, the first of a two-year deal at the veteran's minimum salary, making just three brief appearances after Feb. 1.

"He's a giant," commissioner David Stern said Wednesday at the NBA finals in Miami. "He's physically imposing; he has an imposing smile. In the game, he imposed his will, and he has done it for quite a long time. It's been a great run, and we're going to miss him greatly. We hope we can find ways to keep him involved in the game."

O'Neal, 39, retires fifth all-time with 28,596 points, 12th with 13,099 rebounds, and a .582 field goal percentage that is second only to Artis Gilmore among players with more than 2,000 baskets. His free throw percentage of .527 - well, now is not the time to dwell on that.

"I'm a little bit sad," said Heat president Pat Riley, who also coached O'Neal when he won a title in Miami and watched Kareem Abdul-Jabbar, Patrick Ewing and Alonzo Mourning when they retired. "It's been an honor to be part of coaching great, great players. And he will go down as one of the greatest of all time."

Appropriately, O'Neal's retirement became the No. 1 trending topic on the social networking site he embraced by early evening, and his former teammates and opponents took to Twitter to wish him luck.

"Shaq not only dominated the game of basketball but also dominated off the court w/ his big personality. Hes 1 of the greatest entertainers," Magic Johnson said. "Thank you Shaq for leading the Lakers to 3 titles. We loved every minute of it!"

O'Neal spent three years at Louisiana State and was the big prize when the Orlando Magic won the 1992 draft lottery and selected him first overall. He took them from the lottery to the playoffs in two years, and then led them to the NBA finals in his third year before they were swept by the Houston Rockets.

O'Neal signed with the Los Angeles Lakers in 1996 and had his greatest success there, winning three titles alongside Kobe Bryant and coach Phil Jackson. But amid tension between O'Neal and Bryant after a loss to the Detroit Pistons in the finals, O'Neal was traded to the Heat in the summer of 2004.

"I often wonder how many they would've won if he stayed," said Johnson, the Lakers Hall of Famer.

Lakers owner Jerry Buss, who decided to break up the tandem and keep Bryant, thanked O'Neal for a "long and amazing career, with a huge impact both on and off the court."

"His contributions were significant to the entire NBA, but we specifically appreciate what he did with and what he meant to the Lakers during his eight years with us," Buss said. "We have three championships that we wouldn't have won without him, and we will forever be grateful for his significant contributions to those teams."

After 3? years in Miami, a tenure that included his fourth NBA championship, O'Neal became a veteran for hire, moving to Phoenix and then Cleveland and finally Boston. But he couldn't deliver another title for Steve Nash and Amar'e Stoudemire with the Suns, with LeBron James with the Cavaliers, or with the Celtics' Big Three of Kevin Garnett, Paul Pierce and Ray Allen.

At each stop, he endeared himself to the fans and his new teammates with his effervescent smile and playful attitude, including the habit of adopting a new nickname he felt embodied his role with his new team. In Phoenix he was the "Big Shaqtus"; in Boston, the "Big Shamroq."

"What a career for Shaq Diesel!!" James wrote on Twitter. "The most dominating force to ever play the game. Great person to be around as well. Comedy all the time!!"

O'Neal connected with more than 3.8 million followers of his Twitter account, keeping them informed of his "random acts of Shaqness" - like sitting in Harvard Square, pretending to be a statue, or going out in drag on Halloween.

But his off-court persona couldn't disguise the fact he was getting old, and while he showed he could still play with younger opponents, he couldn't manage to stay on the court with them. He missed a week in November with a bruised right knee, a week in December with a calf injury, and another in January with a sore right hip.

He returned for three games - a total of about 34 minutes - before missing the next 27 games with what the team called a sore right leg. Although the injury was originally expected to keep him out just a few games, his absence stretched to more than two months.

He returned to play in one more regular-season game, but lasted just 5 minutes, 29 seconds before reinjuring the leg and limping off the court. He missed Boston's entire first-round series against the New York Knicks and made two appearances against Miami, a total of 12 minutes, and scored two points.

In all, O'Neal averaged just 9.2 points, 4.8 rebounds and 20.3 minutes this season - all career lows.

"I'm glad that he retired. I think it was time," former guard Tim Hardaway said. "He was hurting his legacy. You don't want to see anybody hurt their legacy when they're going out. I think a lot of people are happy he didn't go through that pain of waiting too long. And I think it was tough for everybody to watch Shaq when he was playing hurt like that at the end of this season."

And that left O'Neal in the market for a new nickname.

After announcing his retirement, he asked fans to give him a nickname that befit his retirement. He reported at about 5 p.m. that "The Big 401K" was the leader.

"I know you can do better, though," he said in another video. "I'm here all day. I'm retired."