Concerts and Conventions:
While the Hollywood Bowl in Hollywood has more ambience, and the Rose Bowl in Pasadena offers a chance of seeing concerts with 90,000 of your closest friends, the city of LA has its own concert venues that are worth exploring.
Nokia Theatre at LA Live: Part of the $2.5 billion LA Live project, the Nokia Theatre is located near the Staples Center. The 7,100 seat venue hosts annual events such as the ESPY awards show and major-name concerts.
Staples Center: While primarily a sports venue, Staples Center also hosts a large number of major-name concerts with its 19,000 seat capacity.
LA Convention Center: Within walking distance of the Staples Center, the massive convention center hosts everything from the LA Auto show to the adult film industry's Erotica LA convention.

Sports:
LA has great opportunities for seeing live pro sports.
LA Dodgers: Dodger Stadium Who wouldn't want to grab a Dodger Dog and get a nice sunburn watching a game of baseball? Don't forget to wait until the 2nd or 3rd inning to show up, as the locals do, and to get the genuine LA experience, leave in the 7th inning - traffic is atrocious getting out of the stadium, and some Dodger-stadium visitors will be gone before the 7th inning stretch. For $35 you can get all-you-can-eat hot dogs, sodas, and nachos at the Right Field Pavilion.  edit
LA Lakers: Staples Center. Do they need an introduction? They are the most popular basketball team in the city. Prices are very high (the most expensive ticket in the NBA) but you will rarely be disappointed with Kobe Bryant, Pau Gasol and the beautiful Staples Center.
LA Clippers: Staples Center. The Los Angeles Clippers are a rising NBA team. Tickets are slightly cheaper than Laker tickets. The basketball season runs from late October to June.
LA Kings: Staples Center. LA's hockey team - they need your support, hockey's not at the top of most people's list in California.
LA Sparks: Staples Center. LA's women's basketball team - they especially need your support! A good, inexpensive family outing and a chance to be shown that women are just as capable of dazzling the crowd with their athletic prowess as men!!

In addition, baseball's LA Angels and hockey's Anaheim Ducks play in nearby Anaheim, and the city's two soccer teams Chivas USA and the LA Galaxy (featuring David Beckham and USA World Cup star Landon Donovan) of Major League Soccer play at the Home Depot Center in Carson.