The most obvious choice, for English-speakers, is For All the Saints. Frankly, it is a masterpiece. Ye Watchers and Ye Holy Ones, although often looked, may be still more spectacular in its summoning of those who enjoy the Beatific Vision. We have already professed our affection for Bernard's O Quanta qualia, best known in John Mason Neale's translation as Oh, What Their Joys.
Which is to say: a decent hymnal offers these three songs, they are wonderful, let's all sing them. But if, for some reason, your particular parish wants to explore lost and lesser gems, the pickings grow quickly slim. You might at least consider Jean de Santeul's Vos sancti proceres, translated by Isaac Williams.
This is a modern hymn, by churchy standards -- de Santeul lived from 1630-1697. Although trained by the Jesuits and professed at St-Victor, he was apparently "a fountain of levity," remembered after his death for a variety of scandalous antics. Williams published a popular volume of Hymns from the Parisian Breviary in 1839. Despite translating many hymns, Williams is not by any means our favorite poet, and we wish that we had a Latin original for comparison or, better, retranslation. But we don't.
The hymn is short and charming, quickly describing a few saints by category and ending with a sentimental allusion to Isaiah:
Ye saintly choirs, that round the regal seat,
Through Heav'n's eternal palace, endless throng,
May we with voice for mortal not unmeet,
Join your eternal song.
Myriads of spiritual hosts the throne around
Stand with their votive offerings, day and night;
There doth the herald Baptist dive profound
In the deep flood of light.
There they, whose voice sounding Christ crucified,
Like thunder went about from strand to strand,
With the anointed Prophets by their side,
The twelve great Preachers stand.
There in their purple stole are Martyrs seen,
And Virgins white that knew no earthly flame,
Like roses which with lilies blend between,
The victim's wreath to frame.
They who have fed their flocks are feeding there
In God's own fulness, brought for ever near;
And they who wept,—a Father's calming care
Wipes away every tear.
The meter is a damnable 10.10.10.6. We aren't sure what tunes it could be sung to, but perhaps readers can offer suggestions.