Bryan Cranston did not receive an Oscar nomination for portraying Shannon in Drive.
Cranston portrays Shannon as really a likable loser. Shannon repeatedly and unrepentantly remarks about how he really does use the driver for his own exploitation, but Cranston portrays the technically speaking less than positive aspects of Shannon with a certain warmth and smile. It is easy to see why he could so easily take money from the driver, as well even from gangster Bernie Rose (Albert Brooks), becuase Cranston has a genuine though low key charm in his performance. Rose states that he liked having Shannon around, and Cranston makes it believable that he would say that.
Cranston very effectively acts as a bright spot in this film which is filled with very seedy characters throughout. Cranston does it well with a great deal of enthusiasm, and more importantly he is able to do this despite that Shannon really is not entirely not a bit of a seedy sort himself. Cranston though is consistently jovial in the seedier qualities found in Shannon, even in the moment where he tries to convince the driver to share the money from a botched money Cranston still makes Shannon likable in that he shows that really Shannon can barely contain his understandable self interest.
The big reason that Cranston makes Shannon's self interest understandable is that he is able to portray a tragedy within Shannon, as Rose says in the film that Shannon never had a lot of luck. These are subtle, and short moments in Cranston's performance but are quite powerful when they do come about. These are mostly in small reactions like when Rose's partner mentions Shannon legs, and in just brief moment Cranston portrays a far deeper sadness within him. Cranston plays it well portraying that his more seeming overt happiness in the other moments, although while not a facade, is very much a way of him trying to overcome his troublesome past.
Shannon really is a fairly small role in the film, and he comes in and out, but Cranston makes an impact within the film whenever he does appear. He creates Shannon into an endearing character, as well as heartbreaking in the end of the film. He combines the various elements into making Shannon a compelling character that adds well to his film. Cranston makes what happens to Shannon in the end not just something that is part of the film, but instead makes it so the Driver's final actions all the more poignant and powerful. Cranston works extremely well with his somewhat limited screen time and turns Shannon into far more than he would have been in lesser hands.