I love ligatures. The merging of two characters within a typeface to create a more confortable spacing and natural flow for the readers eye. Something practical and strangely beautiful. Even the non practical ones; some seem totally unnecessary, but I love them even more.
Now here is a really innovative use of the ligature system within OpenType fonts. Chartwell, "a family that explores the use of OpenType to interpret and visualize data." Type in numbers - get an infographic. Genius.
TK Type for more info and to buy your copy.