Nice collection so far... Well, as for me:
1. If given a direct route on contact (being still in someone else's airspace) eg. proceed "Fix 1-Fix 2", reading it back and then keeping flying on the airway - bare in mind that I might do it for separation not only to help you with the direct...
2. Requesting a higher level when there's opposite tfc 1000' above 10 nm out, and same track traffic 2000' higher just on top - of course requesting THAT level... Just wondering if you're looking at the TCAS before keying the mic
3. When cleared to eg. FL260 reading back "descending two-six-zero" - which could be "to six-zero" as well... Then I ask to confirm cleared level is FL260? "affirm, descending two-six-zero"...
4. As already mentioned before - any kind of(mainly frequency change) readback without callsign...
Keep up the good work, all the bests for everyone!