Simultaneous Buck-Boost or Flyback Regulator - Help Selecting Chip
A traditional buck-boost converter (and the Cuk converter) invert the input polarity, so you can get -12V for your 4-25V input voltage range.  What's confusing is that there are also buck-boost converters that usually use a 4 switch topology to either buck or boost depending on Vin, and do not invert the polarity. (As does a SEPIC converter.)

A flyback can also use the transformer turns ratio to give outputs above and below the input voltage.

A charge pump's operation depends on the configuration of the switches and the capacitors and the control scheme.

You don't say how much current you need, but something like this part from LTC could work http://cds.linear.com/docs/en/datasheet/31151fa.pdf