Going with Expanded Format ARBs:
Bilbo, Bearer of Things Burgled is the centerpiece of his own deck strategy, which normally chokes and takes advantage of
Consorting with Wizards.
Boromir, Bearer of Council is still probably the weakest of the lot, having a pretty severe disadvantage... although I have seen some players use him effectively in Gondor tank decks with
The One Ring, The Ring of Rings to mitigate his skirmish penalty a bit. I've also seen him used with
Denethor, Last Ruling Steward decks which play a lot of
Athelas and
Kingsfoil that can heal him.
Faramir, Bearer of Quality is sometimes used in Madril decks, or in combination with
Pippin, Wearer of Black and Silver. His skirmish penalty can actually help out Madril decks. if you put
The One Ring, The Binding Ring on him and play
Stewards' Legacy, you can also cancel minion special abilities in Maneuver.
Galadriel, Bearer of Wisdom is a staple in Expanded Format Elf decks. She has no skirmish penalty, you can get her power up pretty decently, and she's good at holding a bow and using
The Splendor of Their Banners or
The White Arrows of Lorien.
Gandalf, Bearer of Obligation is one of the most powerful Expanded decks out there, in spite of his rather severe movement penalty. Clever players have found ways of dealing with that, and as long as you can keep his resistance up, he becomes a very powerful character with no skirmish penalty.
Gimli, Bearer of Grudges is most often used in Expanded Dwarf decks, especially Dwarf Choke, for the reasons Bib already mentioned.
Isildur, Bearer of Heirlooms is often used in Knight decks (for obvious reasons) and in Wraith decks, because his skirmish penalty can actually help power up your Wraiths.
Sam, Bearer of Great Need, is also the centerpiece of his own deck strategy which tends to choke and use lots of Hobbit Allies, Followers, and
No Visitors.
Smeagol, Bearer of Great Secrets is the centerpiece of his own strategy as well, which often runs Smeagol solo, or with just one other guy (usually
Faramir, Son of Denethor). It's often paired with a Ninja Gollum Shadow, and takes full advantage of
Naked Waste.
And yes, when you start with them as Ring-bearers, you ignore their twilight cost.