I am a bit of a butterfly and cannot stay faithful to one. At this moment I'm in love with layer masks and adjustment layers.
Layer masks because they open vista's of unforeseen possibilities, and adjustment layers because they do everything the Image>Adjust menu does, but without increasing your file, without making changes definitive and with the possibility to attach them to the layer(s) you choose.
A filter I don't like for example is the Solarize filter. If you open any RGB image, copy your background layer and invert the copy, you can use for example the Difference and the Luminosity blend mode to get far better results.
Of third-party plug-ins, I love to play with the Kai's Powertools I have (5, and 3 were on the same CD) but I rarely see real use for them.