Only Turkey.
it shares land borders with Albania to the northwest, the Republic of Macedonia and Bulgaria to the north, and Turkey to the northeast.
The Aegean Sea and the Mediterranean Sea both border Greece and Turkey.
The Balkan countries are Albania, Bosnia and Herzegovina, Bulgaria, Croatia, Greece, Macedonia, Montenegro, and Serbia. A coastline is another word for a coast or border with the sea, so this question asks which of the Balkan countries are landlocked. Most of these countries border either the Aegean Sea, the Ionian Sea, the Adriatic Sea or the Black Sea. However, both Macedonia and Serbia are fully landlocked with no coastline.
There are two countries that border both Switzerland and Germany: Austria and France.
There is no sea the borders both the Mediterranean and Black Seas. In order (by water) to get from one sea to the other, you need to pass through the Aegean Sea, the Dardanelles Strait, the Sea of Marmara, and the Bosporus Strait.
The two countries that border both Switzerland and Germany are France and Austria.
There is no current capital that borders both the Black and Mediterranean Seas as the distance between them at their closest point is around 500 kilometers or 300 miles. However, Turkey, the only country that borders both Seas has an inland capital at Ankara. During the days of the Ottoman Empire (1453-1923), Istanbul, the only city on both the Aegean Sea (an arm of the Mediterranean Sea) and Black Seas, was the capital of that state. Istanbul still remains Turkey's largest metropolis even though the authority of government remains vested in Ankara.
Both Azerbaijan and Turkey border both Armenia and Iran.
Scotland and Wales both border England.
Latvia and Russia
Both Guatemala and Belize have a border with Mexico.
Alaska has both a land border with Canada and a Maritime border with Russia.