I go through phases getting off on first one then the other. First, I will say that I get off on the substance as well as the act.
I was taught as a child to refer to it (and the act) as "Tinkle" and only to utter even this word to a select few relatives in secret. Otherwise a need to relieve myself was referred to as "I need to go to (or use) the bathroom". Other words I had heard other children say such as "Pee", "Pee Pee" and "Wee-Wee" were strictly forbidden. Later, in school I of course was exposed to all the other vernacular references as well as the more "proper" "Urine" and "Urination".
As I said, the ones I "like" varies with my mood. Sometimes, I will simply get tired of hearing or reading a certain word for it and will try others until I hit upon the one that "really rings it" for me.
Then, there's the private (read sexual) and "polite company" usages of the various terms. In public situations I just say "I need to use the restroom" but my private world of urolagnia is much more varied and variable.
The words that seem to arouse me most often are (in order of preference) Tinkle (the act and the substance). Pee (the act and the substance). Urine (the substance). Pee Pee (the act and the substance). Piss (the act and the substance).
I'm sorry if this got way too long and involved.