my favorite feature is not necessarily a complication ...
... but i really
really appreciate extended power reserves, preferable paired with a discreet pr-indicator. especially if you have three or four waches that you rotate, it's really cool if after a week of idling in the watchbox the watch du jour is still running strong :o)
my favorites in the 'attainable' range are the jlc 8-days-movement like in the pam190 or the iwc 5001-series 7-days-movements, and the parmigiani hebdomadaire-models . other contenders in the more unrealistic realm are the 10- or 15-day pr-models from various high-end houses.
other than that, i enjoy perpetual calendars and minute repeaters/sonneries ... the former for their practicality (provided you have an auto-movement and a watch winder ;o) heehee...) and the latter for their total coolness ... a well-executed chining watch with a nice ring always fascinates me :o)
oh, and finally i think erotic automatons are vastly underrated LOL :oP

cheerio, johannes