I really like the Westfold Horse-breaker. It is overcosted and that defense strength is pointless, but that ability is awesome and game-saving. Think about a pumped up Gimli, Eowyn, or Treebeard. And it synergizes with the Rohan discard mechanics.
Dunedain Mark is a nice cheap attack boost, and one of the more splashable options. It has synergy with the Weather-Hills Watchman and Rune-Master for easy searching and affordability. Plus, like the other signal,s it can change control.
Bilbo Baggins is rejected mostly due to his insanely high threat cost. But an extra card per round is inarguably powerful and he can still take an action (though granted, that won't be much). He has good synergy with Protector of Lorien for hand pruning. He has very good potential as a Voltron deck target due to in-sphere access to a Burning Brand and Fast Hitch. With Steward, Blood, and Fire,and Lay, you'll want the songs to play them; which warrants Fireside Song. He's got a good deal more to offer than any of you know, including himself.
IT'S GANDALF! AND GANDALF MEANS HIM! Seriously though, Gandalf is an insanely good card. For five resources, you get four stats, an average of four something from his ability, and a trigger to Eomer, Imrahil, etc. With sneak attack, you're saving four resources, and can still play Gandalf again next round. He's seen decreased play with the release of two other versions of Gandalf, but still, insanely good.
Self Preservation is a neat healing ability, if more expensive than most. But it's repeatable (unlike most other healing attachments), and not susceptible to direct damage (like most healing allies). One thing of note is that it will only heal the attached character, unlike the DotN.