Russia-Finland
Mongolia-Russia
Note the Soviet hammer and sickle on one side, the Mongolian Soyombo on the other.
Georgia-Russia (no, Sarah Palin, the Caucasus Georgia)
China-Russia (Heihe and Blagoveshchensk), Russia is the near side, and the border is the Amur River
China-Nepal (Mt. Everest in the left in back)
China-Pakistan (north side of K2) This is one version, the Chinese mountain borders have several alternate paths no one will agree on
UAE-Saudi Arabia (from mountains to the desert!
)