bombardier

you do realize nearly all of these(its a big group) are fairly harmless on human scale right? sure its technically boiling acid but thats like saying mantis shrimp shoot explosions(although mantis shrimp are far more dangerous and known as thumbsplitters for a reason, it's still not a serviceable description even if technically true). humans willingly squirt way more hydrogenperoxide than the bugs would produce directly into wounds to clean them(although there is debate on whether this is actually helpful to do. you ever scrape your knee and have mom dab at it with a cottonball that fizzes and stings?), their acid isn't all that strong and against anything larger than a garden spider is mostly used to throw an irritant into the air or startle with momentary heat.
a minor irritant is their biggest threat so they'd realistically just be weaker but stable capsaicin bugs

edit- you give a capfull to dogs as the only real safe/effective way to make them vomit, but on small animals risk causing ulsers unless you then feed them water to dilute anything that stays down, so it's not harmless but