Cum turns me on, albeit my own or someone elses. Ive had many cum kisses of my girl and she has even text me in work, told me to wank off and eat my cum for her, its a power play and we both love it.
When I masturbate I usually think about my ex girlfriend and bring up the pictures of her masturbating (which she did a lot), she has the most beautiful 'butterfly' labia I have ever seen and it still makes me hard.