With no permanent deacon, we have a revolving door of occasional visiting deacons, usually not of our diocese (or even jurisdiction). The most common is a deacon whose family lives nearby. Multiple heirarchical commemoration mishaps have occurred, including chanting the wrong city for the bishop ("Atlanta", instead of "Dallas") and forgetting the name of our hierarch altogether and having to have the priest whisper it to him (both during the Great Entrance).
Gospel Reading mishaps occur because of this as well, since us poor servers never know where the deacon is going to read from (as it could be from the solea or from the bema). Once, I recall all of the servers setting up for a reading at the solea, just to have the deacon exit the beautiful gate and walk right past them to the center of the nave. All of the servers then had to shuffle over to the new location.
Our priest accidentally set his service book on fire one morning during the psalter reading at Daily Matins. He got it put out and still uses that book, but there is one page that is almost entirely missing, which we see him flip by every Saturday night during Vigil, which always causes me to chuckle.
Here's one that I did myself: While serving at Vigil, I realized after God is the Lord that a new charcoal had not been lit (it is our practice to light a second one during the Six Psalms) and so I rushed to get it lit, which didn't quite work. I had to hand off the dying censer to the priest after the troparia were sung, but another server helped me to place the new charcoal on top of the remnant of the first (which also had incense on it) along with a little more incense so the priest could cense the nave (when he needs it, our priest will cense the altar, then stop by where we keep the incense and hold out the censer for us to "refill"). However, what we didn't think of was the fact that we had created, in essence, an "incense sandwich" with the two charcoals being the bread...and then topped it with incense. This caused not only the new incense to burn, but the old incense to burn VERY RAPIDLY. This caused WAAAY too much smoke, and even ran one family that is particularly sensitive out of the nave for the rest of the service. Suffice it to say, as soon as the priest finished with that censing, we fixed our error.