Worth to note: there's a critical difference between x! and anything we've brought up so far: x! could be used as an L-value:
x! = value
x!.mutatingFunc()
x![1] = value
x!.field = value
whereas
try x ?? throw error = value
or a similar syntax would result in:
// 
Cannot assign to value: binary operator returns immutable value
Would be cool if the "throwing optional unwrap" equivalent supported L-value usage scenario.
In light of the L-value issue, here's another suggestion: introduce a special built-in postfix ^ "operator", that for all intents and purposes works like ! except it throws on nil instead of terminating the app:
try x^.mutatingFunction()
try x^ = value
try x^[1] = value
try x^.field = value
value = try x^
When the value is nil it'd throw some fixed non customisable "Nil" error.
That'd require a compiler change as it can't be done by current language means.
Similarly as^ could be a throwing version of as!