The AI had a Shaper Guildmage on board. It had an Ancient Den and a Vault of Whispers as mana sources to activat it's abilities. It attacked with a Spire Serpent into a horde of creatures (very unusual). I blocked in a way which would let the serpent survive and kill things if it gets first strike, to test Shaper Guildmage. Nothing happened, the serpent died.

Then, after combat, one of the guildmages gave a random Omenspeaker first strike for no reason and no gain.

In another match, I had no creatures on board and the enemy had 2 Shaper Guildmage and an Omenspeaker. I only attacked with the Omenspeaker, into an empty board, for 3 turns. Then it lost the Omenspeaker, equipped one of the Shaper Guildmages, and still didn't attack with them. Then, much later in the game, it attacked with them for an alpha strike.

Or just now, there's only one Shaper Guildmage in play, it's equipped, and it doesn't attack. There's nothing else in play but that and some lands on both sides.

And now one gave one of his dudes first strike in response to my black lotus during my turn.

Not going to try to figure it out on my own.