The outlaw synergies have only been introduced recently, but they have a lot of depth since assassins, mercenaries, rogues, warlocks, and pirates have years of support, not to mention how cracked Treasure tokens are
Battle cards have a pretty daunting task before them: to do something that no other already-existing card type already does
For example, if youre using a commander like Gishath that cares about a single creature type, include cards like Icon of Ancestry that let you choose a creature type to apply an effect to, as well as cards that care about your specific creature type (like Thunderherd Migration in the case of Gishath)
Sin, Spiras Punishment Sin is a rather interesting payoff for decks that are graveyard-centric
When a Field Spell that is already face-up on the field activates its effect (Quick Effect): You can shuffle 1 of your monsters that is banished or in your GY into the Deck, or if that monster mentions that Field Spell, you can Special Summon it instead
They often end up being the most valuable from any given set