satoshi (written in full or as "sat") (for small amounts).
ExampleAmount: 0.1 mBTC (0.0001 BTC, or 10,000 satoshi).
Interest: 1% (0.001 mBTC (=0.000001 BTC or 100 satoshi)).
I think I prefer sat > s@. It's faster to type and requires the same number of keystrokes, at least on a QWERTY keyboard. For touch typers, S and A are both on the left-hand home row whereas T is a slight movement away from F. @ requires both a wrist movement from the right hand & pinky as well as a stretch from the left hand ring finger to the @ sign.