Poll: What database do you use in production?

Is there a good primer for someone who's curious about the differences between different databases? My work made the decision to use MS Access long, long ago, but I have no idea what that means vs. MySQL, MongoDB, etc. (other than the fact that it's a proprietary system).

I know a lot of people always seem to be complaining that mysql is not powerful enough in a production environment, specially the people with large websites complaining that it is not scalable enough. Personally, I feel that that is not the case in most instances. Only a very little amount of people ever have to deal with these issues and mysql is performs really well for rapid development, which, in most cases is what people want and need to get their idea up and ready.

Missing entries:

SQLite (yes, it is useful in production)

kdb+ (it's kind of specialized, but so are vertica and greenplum)

HyperTable (if hbase is there ...)

Tokyo/Kyoto Cabinet (if redis is there ...)

On second thought, this might be already too spread out, too many options already for a meaningful survey