slide braces - one nice percussive effect is to hit the slide braces together. The low thump in Puddles & Crumbs is that sound. Since this action causes the bell to resonate strongly, it's something that either with a clip on mic or a contact mic, could be processed very easily (like Katie's addition of a huge reverb tail, etc.)
trigger noise - there's a lot of this in Katie's piece (which is the amplified double-clicking), Eric Wubbels's new duo (starts around 6:13 in this movement), and a significant part of my version of Michelle's three part construction. Michelle's I feel like has the most obvious material use of this sound, but we could potentially come up with more!
consonants - I can just do any voiced or unvoiced consonants into, or near the mouthpiece. These are pretty much unpitched - not much resonance of the instrument is activated. 't', 'k', 'f', 'p', 's', 'sh', 'ts' are available.
tongue rams - basically this is adapted from flute tongue rams, it's totally the same technique/physical action. However, it always sounds at the fundamental, there's no weird M7 transposition. I can get a relatively large dynamic range, and iterative speed can get pretty fast! probably around 16th's at 132-144 or so. These can also be executed either by exhaling or inhaling - they have fairly distinct timbres, so they could definitely be used as separate materials. The inhaled version, when repeated, also gets a lot of air noise in the mix, resulting in a kind of high pitched whistle-tone, which is a result of the tube acoustics...
The louder I get the brighter they sound, which starts emphasizing higher overtone content (but only subtly). Like the flute technique, I can have a pickup note of air beforehand, or draw it out fairly long, but this sound can either be very flat and dry, or have that rebound or ricochet like effect.
Inhaled slaps will necessarily have a slightly longer tail at the beginning since the slap is at the end of the breath. But I can do these either way - alternating quickly is really tough though, I'd proceed with caution. I can basically link them up though - alternating inhale and exhale every 5-7 seconds or so, and create a constant rhythmic stream of attacks.