I love ligatures, they add a special pinch in a simple and boring text or logo. infacts, after a research I did yesterday, ligatures are used mostly in logos and lettering, as a stylish touch.
each font has different ligatures, but they basically have the f ones.
is nice to see sans serif font's ligature.
there are some fonts that create some ligatures automatically, like these
my logo is a ligature: s and t are connected by a c, that stands for my first name (the one I don't use), its presence but subtle for this reason.
other logos are pinterest and vine for social media
boat is a magazine and trafiq is a club and restaurant in Budapest
here a nice tumblr that collects some interesting ligatures.