As much ciminally insane as he is intelligent, The Joker is the one foe Batman has never truly been able to figure out. He has tormented The Dark Knight for years, even killing (The Jason Todd Robin) or crippling (Barbara Gordon aka Batgirl) some of his allies. What is perhaps most telling about Joker is he never seems to have any ultimate goal for his crimes. Other supervillains crave power, money, inluence, immortality, or all of the above. Joker wants none of that, and is seeminly happy with chaos just for chaos's sake.
The true origin of the aptly named Clown Prince Of Crime is still unknown, with the exception that while he was known as The Red Hood, there was a showdown with Batman which ended in him falling into a vat of toxic chemicals. Inexplicably, the former Jokey Gillis was not killed by the chemicals, but was permanently discolored and disfigured. His insanity breaking at this point proze his mouth into the demented smile while his skin was dyed white and his hair green.
Aside from his genius intellect and psychological tactics, The Joker's main traits are his chemistry abilities. He can make bombs or lethal chemicals seemingly at the drop of a hat. He's also shown to be quite competent with most firearms and technology.
Cobb is a master in the art of extraction, which consists of stealing his mark's ideas by infiltrating their dreams and stealing valuable information from them. He is well known in the black market because of his level of expertise in the field of extraction. Cobb was implicated by his wife Mal in her death in a letter she filed with their attorney; as a consequence he's a wanted fugitive who can never return to his home. He is portrayed by Leonardo DiCaprio. His Totem is a spinning top. He uses a Beretta Px4 Storm consistently throughout the film, also using a suppressed Blaser R93 LRS2 sniper rifle during the third level of The Fischer Inception Job.
http://inception.wikia.com/wiki/Dominic_Cobb