Syr Gwyn, Hero of Ashvale

• WOTC Official Reminder Textofficial rules
  Vigilance — Attacking doesn't cause this creature to tap.
• WOTC Official Reminder Textofficial rules
  Menace — This creature can't be blocked except by two or more creatures.

• WWizards of the Coast2019-10-04
  Official Ruling
  If Syr Gwyn leaves the battlefield after an equip Knight ability has been activated, that ability still resolves even though the Equipment has lost that ability.
• WWizards of the Coast2019-10-04
  Official Ruling
  Syr Gwyn's triggered ability triggers once per attacking creature that's equipped, regardless of how many Equipment those creatures each carry.
• WWizards of the Coast2019-10-04
  Official Ruling
  Whether the target creature is a Knight is checked only as the equip Knight ability is activated and as that ability resolves. If the creature somehow becomes a non-Knight creature later, the Equipment remains attached to it.
• WWizards of the Coast2019-10-04
  Official Ruling
  Equipment you control still have their other equip abilities in addition to equip Knight .

Rulings via Scryfall