Ingested alcohol.  Rubbing alcohol seems to be fine.

Vantin.  This is a newer type antibiotic.

Monistat.  See the ER Adventure I had at MLO Knitting.

Morphine. Actually, a rare reaction where it causes a headache so bad that other pain seems to pale.

Thus far, it is only this – but with corn being in everything, it is making finding safe medications harder and harder.  For the most part I can tolerate small amounts of cornstarch in pills – but I would get worried if we got to the point of 1/4 cup or more.