The obvious choices have been mentioned (and with others, I'd vote for Fowers of the Forest), but if you are after something a different, how about a Scots piece about a chap who decides his only chance of getting the girl is a neck or nothing gamble in the Army

FAREWELL TO LOCHABER

Farewell to Lochaber and farewell, my Jean,
Where heartsome with thee, I habe many days been,
For Lochaber no more, Lochaber no more,
We'll maybe return to Lochaber no more.
These tears that I shed, they are all for my dear,
And no' for the dangers attending on war,
Though borne on rough seas to a far bloody shore,
Maybe to return to Lochaber no more.

Though hurricanes rise and rise every wind
They'll ne'er make a tempest like that in my mind.
Though loudest of thunder on louder waves roar,
There's nothing like leaving my love on the shore.
To leave thee behind me, my heart is sair pained,
By ease that's inglorious no fame can be gained,
And beauty and love's the reward of the brave,
And I must deserve it before I can crave,

Then glory, my Jean, maun plead my excuse,
Since honour commands me, how can I refuse?
For without it I ne'er can have merit for thee,
And without thy favour I'd better not be.
I gae then, my lass, tae win honour and fame,
And if I should luck to come gloriously hame,
A heart I will bring thee with love running o'er,
And then I'll leave thee and Lochaber no more.

Also

Dave(tam),

I have a different set of lyrics for "Love Farewell" (a hybrid Anglo-Irish song) , Lewis Winstock attributes this version to the 88th Foot (later the Connaught Rangers) in 1809

Come now brave boys, we're on for marching,
First for France and then for Holland,
While cannons roar and men are dying,
March, brave boys, there's no denying,
Love Farewell!

I think I hear the Colonel crying, March, brave boys, there's no denying,
Colours flying, drums a-beating,
March, brave boys, there's no retreating,V Love Farewell"

The mother cries, "Boys, do not wrong me,
Do not take my daughter from me,
For if you do I will torment you,
And after death my ghost will haunt you
Love Farewell!

Noe Molly dear, do not grieve for me
I go to fight for Ireland's glory.
If we live we live victorious,
If we die our souls are glorious.
Love Farewell!

Regards

Walrus

nb: Both songs are to be found in "Songs and Music of the Redcoats")