Hi Joerg,
The Atmel ATtiny11. When I say "cheeseball ADC" I'm referring to its on-board analog comparator. It does have an internal RC oscillator, although it isn't too horribly accurate (for an "accurate" RC oscillator they'd like to sell you an ATtiny12, which of course costs more).
DigiKey gets $0.31 in quantities of 100 or more, so I *think* it's fair to call it a "quarter microcontroller" in large quantities.
---Joel