Misunderestimating Each Other

I often think of Sam's mistrust of Gollum, and how this may have helped spike the last feeble, fitful possibility of metanoia.  That works against the good guys in the short term, at least; though Gollum's free-fall allows the quest to be accomplished.

But I forget that Gollum, in his turn, underestimates Sam, which works to the good guys' advantage:

Not expecting even this simple trick from Sam, Gollum fell over with Sam on top, and he received the weight of the sturdy hobbit in his stomach. (726)