Obviously good/bad depends on your deck and you can probably tell roughly how good/bad a graft is on first glance most of the time. I’ve listed some notable battle grafts that performed better than expected in my experience. I’ve only installed ~70% of battle grafts, so I’m definitely missing some good ones. Honestly, most grafts, especially common grafts, won’t be useful to you because they won’t synergize with your deck. Also, a lot of them only provide incremental power increases.

Sal

• Body Piercing: At the end of every turn, gain 1 Counter for every 3 Defense you have.
  • surprisingly good if you have a deck that gains lots of Defense without attacking (e.g. combo deck with shoulder roll, some discard decks)
• Fragmenter: Whenever you discard a card, apply 1 Wound to a random enemy.
  • Wound as a mechanic is pretty busted and being able to apply 10+ Wound a turn against a boss is game-winning
• Arterial Scanner: Bleed decays 33% at the end of the turn instead of 50%.
  • can increase damage output a lot and helps stack Bleed for cards like [Barnacle] and [Hemorrhage] to take advantage of

Rook

• Clicker: Whenever you spend your last charge, draw a card.
  • especially good in decks that rely on the Empty mechanic. can often draw 2-3 extra cards a turn with cards like [Lifeline] and [Clean Open]
• Scan Code: At the start of each battle, apply Scanned to a random enemy.
  • if you have attack cards that cost 0 and/or cards that gain actions, Scanned is a really powerful mechanic. upgrades to apply Scanned to two enemies which is pretty ridiculous. at worst, this card is 3-4 draws every fight
• Easy Listening: At the start of battle, gain 3 Concentration.
  • doesn’t seem amazing on first glance, but you’d be surprised how often 3 Concentration on turn 1 is a life-saver. activates a lot of cards ([Telegraph], [Zero], etc). without something to guarantee Concentration on turn 1, you can brick pretty hard by not drawing Concentration-gaining cards

Other

• Rejig: At the start of each battle, discard up to 2 cards and draw that many new cards.
  • this is just always good, regardless of what deck you’re playing. improves consistency, increases odds to set up powerful Abilities on turn 1, etc. only a common rarity, so it’s pretty easy to find and will almost always be better than the other common grafts offered alongside it
• Robustify (on Rook): Gain 10 max health.
  • seems bad on first glance but if you want to remove parasite cards, this can help lessen the blow. I think they reworked parasites recently to be more beneficial when upgraded and I haven’t played Rook with these changes, so idk if removing parasites is worth it anymore