i like
font squirrel because they are all free, first of all.
favorites right now are Commando, Courier New, Airstream, and a whole bunch of fancy scripty stuff. but only because they fit artistic themes for some free-time projects i've been playing with.
as far as "default?" idk, whatever the default is. I'm not super picky, like i might think a font looks bad but i'm not going to go out of my way to view something in a different font if i could even change it. i guess as far as preferences go, i like clean and simple and traditional stuff where appropriate, so, like for reading Times New Roman is fine by me, so are most of the made for print fonts. Fonts used in graphic design, whatever works, as long as it's in keeping with the theme.
even comic sans has it's place as lettering for cartoons and comics and whatnot. but times new roman looks like shit in the funny pages. but i guess if i'm writing something long, like one of my erotic historical fictions, i go with either courier or TNR.
(Edited 40 seconds later.)