when should I use a function call without parenteses?

[AsmMan via Digitalmars-d-learn]

In which context do you use a function call without paranteses? 
(considering the function doesn't has arguments or they're 
default, of couse)

I want to know when/why should I use or if it depends only to 
programmer's coding style..

f / baa.foo

versus

f() / baa.foo()

personally, to me, which came from C and C# world I find a bit 
strange use f symbol being f a function but I can get used to it 
very easily.