How to write a pattern that matches all functions

What is the correct way to match a function in an expression in the way that

Cases[Sin[x] Cos[x], _Sin | _Cos, {0, Infinity}]

matches Sin and Cos?

How can I match those functions without list all function names? The following code not only matches functions, but also List,Plus` and so on.

Cases[Sin[x] Cos[x], _?(MatchQ[Head@#, _Symbol] &), Infinity]

Should I express this question as matching a function not in a list such as {List, Plus, Times, ...}?

Answer

Cases[Sin[x] Cos[x], _@_, {0, Infinity}]
(* {Cos[x], Sin[x]} *)


Cases[Sin[x] Cos[x], h_@_ :> h, {0, Infinity}]
(* {Cos, Sin} *)

Note: watch out for expressions that "look like" functions with a single argument:

Cases[Sqrt[x ] Times[Sin[x], w], h_@_ :> h, {0, Infinity}]
(* {Sin} *)

because

Sqrt[x] // FullForm
(* Power[x,Rational[1,2]] *)

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