What do the icons in Xcode 4's debug area variable list mean?
They appear to be:
L = Local variableA = ArgumentS = Static variableV = global VariableR = registerV = instance VariableE = Expression
Here are some links which discuss that part of the interface:
edit: updated with Steve HHH's suggestion
edit2: updated following information from a WWDC 2012 presentation, "Debugging in Xcode" (video no longer available)