Knuth's paper "The concept of a meta-font" (from 1981) has a nice example in which he typesets Psalm 23 ("The Lord is my shepherd ..."), changing the parameters of his font a little with every character. It's sans-serif at one end, serif at the other. (Among other things.) Regrettably, this demonstration doesn't seem to be available online. You can find it, e.g., in Hofstadter's "Metamagical Themas".