Would be great to be able to format texts. Bold, italics, underline and even changing color to add emphasis.
@Koi, it's also a little weird in the sense that it sometimes doesn't work. Once in a while, another character adjacent to the special characters (like underscore) will confuse Skype, and the formatting will not happen. You then have to edit the message and add a space.
You can already do that, although it's a little weird. Like, underscore before and after for italic and asterisk for bold. Although I agree with the color aspects, that would be pretty neat.