Actually I am stunned there are not MORE people admitting they cheated on this thread. I mean we are only human.
Ok, I admit: I recently use the "that was/wasn't my roll" cheat: I generally use spreadsheets for character management and rolling, and as you may know you can request a new roll by hitting F9 in excel, or by just changing any box in the spreadsheet. Now usually, what I do is, I announce an action, and then demonstratively hit F9 to get my roll. But on that occasion there was this one monster which had taken about 200 points of damage already, and had about 10 HP left, and my sheet was sitting on a critical hit with about 160 damage or so, and... ok, I didn't reroll it, I used that crit to absolutely obliterate the remains of the critter. I got to wade in guts, and everyone had fun.
So yeah, I admit I do cheat occasionally as a player
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