I don't mind 'knickers', when used in conversation thats removed from intimate acts. I use the term myself in the everyday when someone blows a gasket and I'll chide them"

'Don't get your knickers in a twist/bind'.
But in an erotic way, '..she slowly removed her knickers'..
it doesn't really do it.. but it can have a place.

'Cock' always works, penis is a bit too 'anatomical'(my brain thinks anatomy).. much like '..her tongue flicked over his corona glandis...' when used in the 'action' part, or when a person is using first term and describing their thoughts, even though yes there are people that do think in term so of 'penis' and not 'cock' etc. 'Prick' is a few notches below 'cock' but more coarse 'sounding'. 'Rod' or 'tool', well! they make me laugh really.Make me think of all the Porky's movies.. 'She saw my tool and fainted' type of thing.

I tend to like 'olde' descriptive English words.. like 'strumpet'.. in describing a female. Sometimes I get tired of reading 'slut' all the time.