1.js

var x = "/x/";

/x/==x

2.js

var x;

// My version
x = function () {
	if (x.times > 4) {
		return true;
	}
	else {
		x.times = (x.times || 0) + 1;

		return x;
	}
};

// Version of @cjwainwright, right version
x = function () {
	return function () {
		return function () {
			return false;
		};
	};
};

x() === x()() === x()()()

3.js

// Very stupid solution, but I have no another idea (yet)
var x = {
	valueOf: function () {
		if (!this.valueOf.wasCalled) {
			this.valueOf.wasCalled = true;

			return 3;
		}
		else {
			this.valueOf.wasCalled = false;

			return 1;
		}
	}
};

x > 2 && x < 2

4.js

var x = (function () {
		var SomeConstructor = function () {};
		SomeConstructor.prototype.a = true;

		return new SomeConstructor();
	})();

delete x.a && x.a;

5.js

var x;

// The first version
x = {
	"[object Object]": "Some primitive value",

	valueOf: function () {
		return this["[object Object]"];
	}
};

// The second, deeper version
x = {
	value: "Some primitive value",

	toString: function() {
		return "value";
	},

	valueOf: function () {
		return this.value;
	}
};

// The third (right) version (not mine)
x = "0";

// The 4th (stupid but brilliant) version (not mine)
x = {};
x[x] = x;

// The 5th version (not mine)
x = {
	"[object Object]": "[object Object]"
};

x[x]==x

6.js

var x = function () {
	x = 1;
};

typeof new x < typeof x

7.js

var x = Infinity;

x - 1 === x + 1