When I'm talking to white people, i say Nigger because its funnier. -- "So me and one of my niggers went to the store, right...."
And if they ask why, it's simple: ...You're white. You're not black, so you don't get to 1) use nigga, or 2) hear nigga from me. I'm going to say the word exactly as you hear it in your White Man mind.
Other than that...I don't use the word that much. Mostly to be a smart-ass, like when I'm arging with White Men --usually, from Seattle/Portland/etc. so they feel they're "down" with black people--I say the word just because I can and they still can't without looking like a wannabe.