cutoffs vary widely by company, and even more so by interviewer. Strong academic performance is one the best ways to display a strong work ethic and an interest in your selected field. If you are from a target or semi-target and want to be safe for the screening, you should work towards a 3.5 or higher. A from 3.0 to 3.5 may give you some difficulties, and a of under 3.0 will make it that much harder to break in. Anything above a 3.5 is considered good and above a 3.7 is impressive. Keep in mind that your doesn't make up your entire resume. Strong or extracurricular activities can make up for a sub-3.5 , but they better be damn good and you shouldn't count on them making up for your .
From a non-target school, things get a lot more iffy. You could potentially break in with a 2.8, but that is the exception, not the rule. You really want to aim for a 3.7+ with strong extracurricular activities. This will help overcome the stigma of attending an unknown school, as the less wild cards you have on your resume the better. Wall Street will not require conformity in every area, but the more areas that match the norm the more likely you are to receive an offer.
Finally, remember that networking can trump all of your shortcomings as a candidate if done properly.