Adagio by Wolfgang Amadeus Mozart for brass quintet, originally for two clarinets and three basset horns (available at Score Exchange). Trumpets are in E♭ and B♭.
“Christus factus est” by Anton Bruckner for trombone choir, originally for choir (available at Score Exchange). This is in four parts: alto/tenor/tenor/bass, although a sufficiently strong player could go without the alto if one isn’t available.
On the way is “O mio babbino caro” from Giacomo Puccini’s opera Gianni Schicchi. Unfortunately, Score Exchange is not cooperating. No matter how long I wait, the website will not finish processing the score. I don’t understand why; it’s one of the simplest things I’ve ever written. Also, I have an an arrangement of Mozart’s Kyrie, not from the Requiem, but an early canon he wrote for five sopranos. It’s done, but in Lilypond, which Score Exchange does not accept, so I have to convert it to Sibelius before I can upload it.