horus:
The word "obstreperous" jumps immediately to mind, but that's too many letters for Scrabble (12 letters). (Seven letters maximum, if I recall, maybe eight if you link to another word.)
Wait... "obsequious" has ten letters. Maybe I'm being "obtuse", but wouldn't that be hard to do in a Scrabble game?
Later On,
D
Technically, you could create
obstreperous by pinning new letters on either end of
strep -- it would take all seven letters from your tray, but would count as a new word. This would make it worth 66 points, not including any bonus spaces. (If any of the added letters are already in place (say, the first 'o'), then it's only worth 16 as most of them are 1-pointers.
Obsequious would be rather hard to make, without relying on isolated letters being in the right place.