Giants have 4th overall pick due to strenth of schedule tie-breaker. Giants had 3rd hardest schedule after Bills and Texans, and therefore they're picking last among all 4-12 teams. Either way, unless they trade down expect Giants to end up with a quality player. My guess is, it'll be one of the four: Eli Manning, Ben Rothensomething, Robert Gallery or Fitzerald. It all depends on what teams in front of us are going to do.
Chargers most likely won't draft a quarterback, but they could trade down with somebody who will. I'm almost certain Arizona will draft Eli Manning, and my guess is Oakland will draft Fitzerald since their receiver core is pretty old and there's a chance Brown or Rice will retire. This leaves the Giants with either Ben or Gallery, all depending on whether Chargers trade down or not.
Well, that's point of view. I could be wrong of course.