A summary of all answers in the thread:
Will mostly do support / brownfield development
Will have to be on-call
No source control or SourceSafe used for source control
Don't do branching of code in source control
Working hours not flexible at all
Using legacy software / tools
no TDD / no unit-testing
Waterfall / no iterative development
You will be the best dev in the shop
(Overly strict) dress code
Obvious monarchy
Too serious / no joking / stressed out
No bug tracking system, or bug tracking 100% owned by QA
Overly restrictive Legal Agreement -- they own what you do at off hours
No blogging policy
No dual monitors
Internet access limited
Disconnected or lethargic or burned out team members
Overtime expected and not paid for
Code / db looks ugly
Yes we're going to implement that but we're very busy now
Too much talk of business priorities / results driven attitude
Not using resharper / will not buy resharper or something like araxis merge etc.
No free time to experiment
Nobody recently went to a software dev conference
Very many clients that come and go (e.g. a marketing company)
No books on shelves or books look not read
"Motivators" posted all over the place
Dirty bathroom / kitchen
No code sharing between team members
No Continuous Integration / no nightly builds
Lack of or little personal stuff on desks
Your potential manager gives you a long lecture
IT is a cost center rather than a production center
no match on 401k
Too eager to hire
Can't use your notebook at work / can't connect to their LAN
No working from home / no remote access
No admin rights on your development box