I'll just keep this as short as possible, since I'm prone to typing forever!
As a FtM, I feel that the word "tranny" is disgusting and should never be used. I had a terrible experience with it a few weeks ago...
I was in a chat room with a friend, no one else was in. She [cis female] mentioned the word 'tranny' as in 'transmission' in a car, and said that someone's had blown, and then followed up by saying 'it made me think of a person [i can't remember if she used a specific gender id] exploding and pearls, makeup, and glitter going everywhere!'. I had to explain to her that it was offensive, she tried to state that she 'didn't mean it that way' despite what she'd just said.
In the end, I had to out myself to attempt to make her see why I did NOT want her using it around me. -sighs- I was intending to never let that get out, but I just wanted to make sure it didn't catch on in our little online hang out...
So yeah, long story short: Please don't use it around me, or every ounce of respect I'd have for you will go down the toilet. =/