In Melbourne, at least when I was a teenager (80s-90s), our nickname for McDonald's was always "Macca's". (Very Australian, that. In fact, "Macca" is a common nickname for anyone whose surname starts with a "Mc" or "Mac").
When I went to China in 1994, it was called 麦当劳 (mai4 dang1 lao2), which literally means something like "wheat merits reward" or some such (any Chinese native speakers out there able to give me a better translation?)
The nickname I've heard used among North Americans is "Mickey D's". Is this specific to a particular region? Are there other nicknames?
I believe the Francphone world, or at least some of it, calls it something like "McDo".
What others have you linguaphiles out there heard and used?