Question: The two I can think of at the moment are Q and Nomad. Q's power is pretty much unlimited, and Nomad restored Scotty's life.

I guess maybe you could argue that Seven of Nine, or any Borg Drone, can also restore life, as Seven brought back Neelix from the dead.

Perhaps you could also include the Guardian of Forever or the Krenim as indirect restorers of life.

Answer: 
Charlie x's alien adopters brought back the people he made "go away"...
To add to Often Right's spectacular list: Didn't Kai Winn poison Gul Dukat as a sacrafice to the Pah Wraiths, but the Pah Wraiths were like "Nuh uh" and then Gul Dukat was like "Wazzup!" and then Kai Winn was all "Oh snap!" So Pah Wraiths, too.