What is the most unusual-yet-effective technique you have discovered or used?

// find the propositions in which A and B disagree
int temp = (A0 & B1) | (A1 & B0);
// if they disagree
if (temp != 0){
    // make a new clause by combining them
    // and removing the proposition where they disagree
    int R0 = (A0 | B0) & !temp;
    int R1 = (A1 | B1) & !temp;
    // do something with the result R
}

Foo &foo;

private string Test(int arg) {
	try {
		//extensive setup

		if (arg > 5) return "too big";
		return "normal";
	} finally {
		// extensive clean up
	}
}