The letter Þ (Thorn) is in modern use in Icelandic, and directly derived from the runic alphabet.
Icelandic, by virtue of having been near completely isolated for hundreds of years, is also the modern language most closely related to old norse, in much the same way American english is closer to the english of the enlightenment than modern British english is.
You still find a remnant of thorn in English to: The "y" in "ye" (e.g "ye olde") is used in place of Thorn - "ye" is just "the" (and should be pronounced as "the").
Icelandic, by virtue of having been near completely isolated for hundreds of years, is also the modern language most closely related to old norse, in much the same way American english is closer to the english of the enlightenment than modern British english is.
https://en.wikipedia.org/wiki/Thorn_(letter)