One of my character ideas that does this kinda thing is a Wizard/Warmage/UM/Archmage. He would combine Warmage Edge with his absurd Intelligence score (remember kids, a Warmage's casting stat is really Intelligence!) to do at least 15 damage per round with a lowly acid arrow. Requires some other static damage boosts to be really effective, though.
If you can stack multiple Acid Arrows on a single target (which makes sense logically, but might not be RAW), then you can rack up lots of damage that way with a couple arrows.
EDIT: Oh, I know... Follow my Awesome Spells link look for the spell Storm Touch in Magic of Eberron. Combine with a weapon that has the Fleshgrinding property, and... I don't remember the name... some property that lets you deliver touch spells through the weapon. I may be thinking about Ki Focus, though, which totally won't work. You can argue to allow Smiting Spell to work, though.