Max Powers wrote in post #15277831
For me, how crooked shots are when shooting hand held despite how straight I believe I am shooting.
Go!
Had that happen to me a couple times
Max Powers wrote in post #15278335
I also forgot to mention....
I can have a 2000$ lens and make it look like a 100$ lens.
That too, particularly in bad light, and when I just want to take a snapshot.
jra wrote in post #15278350
The fact the I can still underestimate my DOF more than I would like.
Often happens with the 85L 
romanv wrote in post #15278559
That shots can look fantastic on the LCD at the time, but utter rubbish on a full screen later.
Those darn Canon LCDs! I only ever use the screen to check exposure/histogram nowadays.
As for my own quirk to add to this? I can take some pretty amazing photos when shooting at my own pace, and only for my own indulgence; but when I have to specifically shoot for someone else, using specified criteria, I'm completely horrible. I make an awful photojournalist.