Blackbeard's third

Which fruit's powers do you think he'll get, if any?

I was thinking Brook, but nah because of needing to meet Laboon.

He could kill an admiral. That could also show his strength, or the strength of his crew. It could be Green Bull. Fujitora wouldn't make sense, since it's too similar to the darkness fruit. Or maybe a zoan makes more sense, as it's easy to imagine using all three together.
Aokiji could be killed by him. That would feel like a waste of his character, but it could happen with Aokiji trying to save Garp. They fought hard, but was Aokiji really trying to kill him? He knew roughly how strong Garp was, so could use strong attacks without actually intending to kill him. Maybe BB will move to kill Garp, and Aokiji will step in, but end up being killed. Hard to see it though, because BB's crew likely can't beat Aokiji and Garp together, unless Garp is pre-weakened enough. Maybe Aokiji fights, Garp is still imprisoned and then Aokiji is killed, just as Koby arrives. Koby and co rescue Garp, but BB takes Aokiji's powers. Koby's ship is escaping and the ice chases it, but he manages to get away.

Imagine if he gets the Noro Noro beam lol.

Loki's

What could it be? Any clues? Has any other giant with a fruit been introduced?

I don't know but it's a top tier fruit. I don't think it would ever happen but it would definitely cement Blackbeard as the top tier of One Piece.

And yeah, Sanjuan Wolf ate one.

Loki or Imu's. Leaning towards Imu.

Unlikely but an interesting route would be Luffy's. Law could resurrect him after the fact.