Risk is for kiddies.
Give me, Dust, Combat Commander, Twilight Struggle, Hammer of the Scots, Advanced Squad Leader, Conflict of Heroes, Diplomacy, Command & Colors Ancients, Here I Stand, We the People, Sword of Rome, Lock 'N Load, Tobruk, Breakout: Normandy, Valor & Victory, Battle for Germany, Storm over Stalingrad, Bitter Woods, The Napoleonic Wars, Nuklear Winter 78, Totaler Krieg!, and Imperial.
Diplomacy is the most tense game I have ever played. It's fairly simple but it's full of lies, deceit, backstabbing, spying, bluffing, double-bluffing, & stunt-pulling. If you want to test your friendship play this one. It makes grown men whine & cry.