Deadpool is the ultimate fourth wall breaker and we all know that.
But do DC have some or any superheroes that break the fourth wall?
Not some random fourth wall breaks but someone who has a habit of doing so...
Yes they do.
As per http://dc.wikia.com/
In the Golden and Silver Age era of DC comics, such characters routinely broke the Fourth Wall, usually as a convenience for introducing a story. After the Crisis on Infinite Earths, comic storytelling took a more mature turn, and few characters demonstrated this ability.
DC Characters known to break the Fourth Wall
- Ambush Bug
- Animal Man
- Black Hand
- Doctor Thirteen
- Kindly Ones
- Madame Xanadu
- Marie Leeds-Thirteen
- Merryman (Myron Victor)
- Mister Mxyzptlk (New Earth)
- Miss America (Joan Dale)
- Phantom Stranger
- Odd Man (Clay Stoner)
One of the famous ones is from Batman: The Animated Series, "Joker's Favor", where the Joker addresses audience (at 13:38):
Until now, DCEU seems too serious for breaking the fourth wall.
In Batman: The Animated Series and Justice League, The Joker addresses the audience, usually as though they were an audience.
In the comics, the Joker breaks the fourth wall in much the same way, addressing the viewer directly. However, given the format, there are other ways to break the fourth wall...
I don't know if you'd quite call it 'breaking the fourth wall' but in her Rebirth solo title Harley Quinn has shown awareness (in conversation with other characters) that she's in a comic strip.