Dark Knight

In an ideal world, Australian actor Heath Ledger would have been celebrating his thirty-third birthday today. Heartbreakingly, he isn't here for it: the actor passed away from an accidental prescription drugs overdose just over four years ago, on January 22, 2008. At the time, the actor was shooting Terry Gilliam's "The Imaginarium of Doctor Parnassus," and the director managed to finish the film with Johnny Depp, Colin Farrell and Jude Law paying tribute to the late actor by joining the production.

Ledger had a rare talent that seemingly wowed everyone he would work with -- Matt Damon, who appeared with the actor in Gilliam's "The Brothers Grimm," recently called him "the best actor I ever worked with" -- and it's hard not to be distraught at the thought of the performances we'll never get to see. But even so, Ledger left behind an enormously impressive body of work for one so young, and in celebration of what would have been his birthday, we've picked out five of our favorite of his turns. There's a number of others that could easily have been included -- his take on Bob Dylan in Todd Haynes' "I'm Not There" is one of the best in the film, for instance, and only just missed this list. But these are the five that we'll always remember him for. Weigh in with your own favorites below.

"Monster's Ball"
"Monster's Ball"

"Monster's Ball" (2001)
Ledger is not in "Monster's Ball" very much. As Sonny, the belittled son of misanthropic prison guard Hank (Billy Bob Thornton), he mainly serves to set up exactly how unpleasant his father is, before, shockingly, committing suicide in front of him. But it's notable as the point where everyone sat up and realized that perhaps Ledger wasn't simply some prominently cheekboned teen heartthrob. The actor broke through in 1999's strong teen comedy "10 Things I Hate About You" with rugged charm, before playing Mel Gibson's son in "The Patriot," and, earlier in the same year as "Monster's Ball," headlining minor hit "A Knight's Tale." He clearly had chops, but his performance as the sensitive Sonny, desperate for love from his father, and taking the bloody way out rather than risk turning into him, made it clear that Ledger had much more to give.

"Lords of Dogtown"
"Lords of Dogtown"

"Lords of Dogtown" (2005)
For a while, Ledger was struggling to match his early heat: "The Four Feathers," "The Order," "Ned Kelly," "Casanova" and "The Brothers Grimm" all came and went (although Ledger is good in both of the latter two, particularly the Gilliam film). But Catherine Hardwicke's "Lords of Dogtown" marked something of a turning point. Ledger plays Skip Engblom, the mentor of the young skaters (who include Emile Hirsch and Michael Angarano among their ranks), a boozy, explosive jester-cum-Obi-Wan figure, and it was easily the best performance of his career to that point -- the film noticeably dips in energy every time he comes off screen. Some snarkily put the turn down as an impression of Val Kilmer, and while Ledger is undoubtedly reminiscent of the actor in "The Doors," anyone who saw "Dogtown and Z-Boys," the documentary on which the film is based, knows how close Ledger comes to the real Engblom. But it's no mere mimicry: journalist Joe Donnelly, a friend of Engblom, wrote after Ledger's death, "He's almost eerie in how precisely he nailed not only the mannerisms, cadence and physical presence of Skip, but also how he raises Skip's spirit."

Brokeback Mountain

"Brokeback Mountain" (2005)
And soon after 'Dogtown,' Ledger's position as a potential titan of the future was confirmed, thanks to his lead in Ang Lee's multiple-award-winning drama about the decades-long, tragic love affair between two ranchers. As Ennis, the more stoic of the central two, Ledger begins with a Brando-like inarticulacy that was much parodied at the time, something that doesn't change how entirely effective it is at portraying a man of enormous feeling, who wouldn't know how to express what he has inside even if society would let him. As he creeps into middle age (effortlessly and entirely convincingly pulled off by Ledger), his self-loathing at what he's done turns into self-loathing at what he didn't do, and it's totally heartbreaking to watch. Ledger never makes Ennis into a martyr: he's quiet, brusque, sometimes even cruel. But it's a testament to his finest performance that you feel so much for him by the end.