Depends on the situation and what i am doing with the font.
If i am writing code i prefer a good monospaced font that is easy to distinguish characters like 1Ll, zero's and Ohh's, etc.
A few decent programmer fonts that i like are Envy Code R, and Source Code Pro.
If i am in Photoshop or iLLustrator then the sky is not the limit. Would be easier to name a font that i dislike than to point out a favorite font.
I tend to dislike serif over sans in design, but even then that is a very general statement that is not always true.
As for CSS and Web fonts i need to invest into a few go to fonts with some healthy backups. Something i haven't really done yet. Same goes for note taking and word. I need to get something good on the eyes for long term reading and writing.