Which brands (fictional and non-fictional) have appeared in the Town/City theme?
I can't believe that nobody else else has posted the most important real company that appears within the LEGO City theme... the LEGO company itself!



There is a good list of promotional sets on Brickipedia, that includes the set theme. Many of the town / city sets include logos or brand names of real-world companies.

Other sets that include real-world brands (some of which don't count as Town / City, according to the Brikipedia themes list) include:


Esso appeared on some very early sets.
DB (Deutsche Bahn) appears on various trains, including 7725.
Sports sets such as, 3432 which has NBA logos on the player's chests, or 65221 that included a Spalding basketball.
1656 Viking Line cruise ship.
Interfrigo, set 147.