TV Guide has reported that Bill Paxton will be guest starring on Agents of SHIELD around February or March for "an arc of at least four episodes".
Paxton will be playing SHIELD Agent John Garrett who is described as "the type who wants to stay out in the field no matter how high-level he gets." This casting sounds like good news for the show since it seems to be drowning in its current case of the week format. A multiple episode guest spot may mean that we might get to see an event that goes over multiple episodes. It could also be an interesting development for some of the characters on the show.
In the Marvel Comics Universe, John Garrett was badly injured in an explosion while fighting Elektra. He was given a cybernetic body by SHIELD to replace his own. The existence of this technology may explain where the show is going with the reveal at the end of last week's episode that Mike Peterson is alive but badly injured.