I've noticed an error in the "Instruction Set Summary" table at the end of AVR datasheets. Not a dramatic one, but the error is present in most AVR datasheets, apparently as the result of copy-paste mathod of datasheet "writing". Although all of those I checked contain this error, I don't know how many of them are actually affected - I could not check them all, obviously. At least one datasheet has this error corrected *partially*, but it is present in its "original" uncorrected form even in the most recent ones.
Please don't spoil the fun and don't post answers publicly until Thursday, 10.September, 16:00 GMT. You can PM me if you want, and I can then post here who got it right ;-)