I'm sure I've heard far more lyrics set to this tune than to any other melody; I only think of them as "parodies" to the degree they fool around with or satyrize the original lyric. That said, I'm going to venture out of my comfort zone enough to put a piece of my own here for the first time; I have no delusions about this making anybody's top 40. but for what it's worth:

For the Unnoticed Heroes

When I was young, so were my heroes;
Now those who are left have grown old;
I hope that the young will find heroes,
To teach them that they can be bold.

One hero may take up a rifle, to fight for the truth and stand bold;
Another may grow old in prison,
Because of some truth he has told.

A hero may die to save others; there's no greater gift one can give;
But sometimes it takes a true hero
To shoulder life's burdens and live.

Some heroes bring something of heaven,
to places touched too much by hell;
Some of them spend all their days caring,
For those who will never get well.

A hero may be any person whose honor you know you can trust;
A hero may be a brave lady   who chooses her seat on the bus.

A hero may be tall and handsome, well-favored and visibly strong;
But my hat is off to the hero, who changes our hearts with a song.

A hero makes up no excuses; a hero asks no guarantees;
Some heroes create timeless beauty,
With paint brushes gripped in their teeth.

When I was young, so were my heroes;
Now those who are left have grown old;
But this world still holds countless heroes.
Each one is more precious than gold.