The ins and outs I am most often asked for, or otherwise suggest, are:
Bridal Chorus from Lohengrin, Wagner (in only)
Prince of Denmark’s March (“Trumpet Voluntary”), Jeremiah Clarke
Trumpet Tune, John Stanley (a flogging good robust jolly little tune)
Trumpet Tune, Purcell
Fanfare in D, Jacques Lemmens (loads of fun, that one!)
Rondeau, Jean-Joseph Mouret (a really good piece that isn’t done-to-death)
Prelude to Te Deum, Marc-Antoine Charpentier
Canon in D, Johannes Pachelbel (in only)
Wedding March from a Midsummer Night’s Dream, Mendelssohn (out only)
La Rejoiussance (Fireworks Suite), Handel
Hornpipe (Water Music), Handel
If your organist is a professional and the organ/acoustics are right, the Widor Toccata is a good stirring piece. Or William Walton’s Crown Imperial in an organ transcription (Orb & Sceptre is sometimes played as well but I think Crown Imperial is better).
Norman Cocker’s Tuba Tune is another good one but needs a suitable solo reed stop. (I think there are other good tuba tunes by Lang and Hollins but need to check my music shelf.)
Not knowing what your building, organ or organist are like, its a bit hard to make specific suggestions as choices are often influenced by the organ spec and voicing (baroque-style, American, English, late 19th-century).
(Incidentally, lots of people ask for the Mendelssohn wedding march, and are surprised if you ask, “which one?” which of course we only do if a bit of a leg-pull is in order. Felix was supposed to write one for sister Fanny’s wedding and didn’t get the job done so Fanny, also a composer, wrote her own, which is now available in print.)
.
!