If Duncan Rime was the last to perform all the deeds and back then there was only eight, adding one would have been nine deeds not ten.
When Zach is sitting in the diner with the Ferrari Owner/Mob Boss the guy behind the Mob Boss has his hat on and then the camera pans to Zach and pans back and his hat is off. Not in time for the hat to be taken off.
The principal's photo has the title "Lieutenant Lester Fuchs" when the uniform he has on in the photo is that of (at least) a master sergeant.
During the party earlier in the movie, the dirty deeds board that shows the "dirty deeds" that have been completed, changes. Deed no.3 changes from "meat on whole wheat with secret sauce? to just "meat on whole wheat" later on in the movie.
Although the list of deeds was supposedly created in the early 80s, there are a few deeds that don't seem to make sense to have existed since inception. "Steal a car worth more than $100K" seems unlikely, because the average cost of a new car in the 80's was $7200. It is also unlikely that the car dealership would have the same inflatable leprechaun or the lodge would have the same night watchmen for over 20 years. It is also believed that the list could have been created in the '70s.
When Zach pulls over because of a flat tire, you can clearly see a crew member's reflection in the car when he comes to a stop.