Off the top of my head I remember for a time that Vitor was "BACK" after almost every other fight.
BJ has been "BACK" a few times
Aldo is now "BACK" after he beat Frankie.
Connor is "BACK"
What other fighters have been "back" the most times and who is currently "back" and that I'm forgetting. 
Lol at screen name, picture and timing of reply above
Vitor Belfort.
This goes back like 15 years. Every time he got a big knockout, people would be saying the old (young?) Vitor is back, baby!
The Bi-Curious Village Idiot -Lol
My goodness, look at the tender embrace between the two on the right.
I back - Anderson Silva
Frank mir
The Bi-Curious Village Idiot -FUCKING /thread
Thiago Alvez
GSP was promoted as 'he's back after being injured!' about 400 times it seemed and now he is back... again
Vrill -100% this.Vitor Belfort.
This goes back like 15 years. Every time he got a big knockout, people would be saying the old (young?) Vitor is back, baby!
Tyson, then Vitor then BJ
Some good ones so far, most notably BJ, Vitor, and Mir.
I would add Shogun to the list.
Randy, Robbie Lawler and Dan Henderson
Chuck had that look back in his eyes we haven't seen for a while ... every time we saw him for the last 3 years.
Probably Eminem. Anytime that dude hasn't been around for a while he comes back with a new track
The Bi-Curious Village Idiot -VU
The Bi-Curious Village Idiot -WOOD
Frank Mir