honestly, and while i may catch flak, i think bodyweight single leg squats(rear leg elevated) are a invaluable addition to anyones program.
That being said, i may be biased, considering i drive, a LOT, and for long durations for work, so my right leg is overworked, but the balance issue/strength imbalance was never more prevalent when i tried single leg work.
While i will never pull a Mike Boyle and espouse nothing but single leg work, it definitely does have its place.
I vote GHR's though
"Before the Beginning, after the great war between Heaven and Hell, God created the Earth and gave dominion over it to the crafty ape he called Man. And to each generation was born a Creature of Light and a Creature of Darkness... and great armies clashed by night in the ancient war between good and evil. There was magic then. Nobility. And unimaginable cruelty. And so it was until the day that a false sun exploded over Trinity, and man forever traded away wonder for reason."
Reigning Undisputed MAB Beard Champion