Great video!  I still need to remind myself that 1 and 20 are not automatic success/failure on a saving throw for sure.  You got me thinking about rule mistakes I still come across, and I came up with another 10.

1) You only get 1/2 of your HD back on a long rest

2) Totem Barbarians can take the abilities of different animals as those abilities are gained (a Totem barbarian who takes the 3rd level Bear power is not limited to the "bear" powers at higher levels)

3) A turn and a round are different things.  A round is made up of several turns

4) Readied actions do not "interrupt", they take place after the triggering action

5) You can break up your movement and your attacks however you like

6) This one is confusing, even to me still: You cannot use the hand that is holding a spell focus to perform the somatic component of a spell UNLESS the spell also has a material component, in which case you can

7) I didn't even believe this one until I saw Jeremy Crawford point it out specifically: The extra attack feature specifies that it works when taken on your turn, which means a readied attack does not include your extra attack class feature (assuming the trigger does not occur on your turn)

8) Surprised creatures can still use their reaction on the round they are surprised.  Similarly, you can take your reaction before your first turn in combat occurs (there is no such thing as "flat footed" in 5e)

9) Unlike weapons, equipping or unequipping a shield takes your action

10) You can use a reaction on your own turn.  So if you get an opponent to use its reaction to move away from you on your turn (with Dissonant Whispers for example) you can use your reaction to take an opportunity attack