I was almost shot for a moose.
I was almost shot as a moose.
I take them to mean the same thing. However, I think "for" here is a restricted usage, as in "He takes you for granted.", "For my part, I’ll be sitting on my front porch in a lawn chair.", etc. These two can be regarded as fixed idioms while "be shot for" seems not.
Based on this I conntrived the following examples:
He was almost killed for a bear.
He laughed at John for a fool.
He accept her painting for a gift.
He kicked away the can for a ball.
These kinds of mushrooms are sold for medicine.
Are they all valid examples? If not, when is for used this way except in fix idioms?