Uses of ruthenium-106?
Expanding @Mithoron's comment into an answer, $\ce{^{106}Ru}$ is used in radioisotope thermoelectric generators that power satellites. Plutonium-238, curium-244 and strontium-90 are the most often cited candidate isotopes for this purpose but other isotopes such as polonium-210, promethium-147, caesium-137, cerium-144, cobalt-60, curium-242, americium-241 and thulium isotopes have also been studied.
Apart from being an energy source, it also finds its application in medicine. $\ce{^{106}Ru}$ is used in cancer radiation therapy, especially to treat eye and skin tumors.