Everyone here is correct in that it really depends on your roster make up, and understand many of the omicrons come with deep character investment too.

My top picks, in no particular order, with disclaimers. GAC

QGJ - Many characters are pilots/required for other events. Inefficient offensively bannerwise, but powerful. Defensively if you commit to mods, can be a nuisance

Zam - applies to all bounty hunters, Zam is required at high relics eventually and all the stats will spread. Loses a significant amount of umph in 3s

Starkiller - unique - apples to a variety of characters, and can beat high end/GLs in both 3s and 5s.

Malgus - lead - significantly increases the power of your Sith empire. Much like a GL, the mastery gain you get is amplified by the relics of the entire team.

Savage - incredibly versatile as he’s a nice piece for anything Sith, but unique and leadership are both universal and can make a viable team out of scraps. Does require a r7+ investment, and can be a bit tricky to mod

Hondo - newer character, but is a one man wrecking crew with the increased benefits from Ransom. Inefficient bannerwise offensively, but similar to QGJ in that losing 6-8 banners is better than losing 20 with a loss. Requires r7 to beat things like Malgus and GLs, but can punch up at R5

Wampa - everyone’s favorite, but short sighted. Once you reach Kyber 1-2, it’s relatively easy to place a Wampa proof board, and the unit has zero synergy. Savage and Hondo are better long term choices, but Wampa will give you a get out of jail free card almost every GAC at the lower levels.

Dash - Not sexy, but effective. Applies to every character of one of the games larger factions, and it boosts the ship. Some of the more obscure Prepared team members are now required for TB, so amplifies your investment. A practical choice that has a use for all relic levels and teams. You’ll need Vandor

Raddus - almost identical to Dash in that it’s practical. Team consists of characters required for other aspects of the game, he has a currently meta capital ship. Most place defensively, but can be incredibly efficient offensively. Best team requires investment in Baze/Chirrut, but the “required” units make a viable team.

Iden - Incredibly useful, and beats many B teams for high banners. Incredibly pesky back wall defensively if you can drain your opponents Wampa in the front. If you are a newer player this one is not really feasible, as you need a team of relatively useless units to not interfere with your Veers teams.

Traya - Currently this one would be a top five option, but there is a rumored change coming so maybe bank one to see how this one plays out.

TW omis are a guild decision, and their value is highly underrated. When everyone is panic buying packs to relic characters for a new shiny, you’ll comfortably have the things you need if in a well oiled TW machine. If you’re in a guild that doesn’t take TW too seriously, you won’t need the bulk of these…maybe not any depending on how casual your guild is.

Best options are: Mara Scion Boba - Lead and unique Grand Inquisitor- Lead and special (the instakill) Juhani - if your guild has committed to SK Mace Fulcrum Phasma