Cards like Sword of the Chosen could tap to give a creature a temporary buff, but were never attached to that creature specifically
1 Urborg, Tomb of Yawgmoth
Aetherstorm RocAetherstorm Roc, Aethersquall AncientAethersquall Ancient, and Roil CartographerRoil Cartographer all do a great job of making large amounts of energy, while Lightning RunnerLightning Runner, Aetherworks MarvelAetherworks Marvel, and Stone Idol GeneratorStone Idol Generator provide some of the best uses for it
I personally really like these, but what are some of your favorites
For example, since having two creatures fight doesn't result in combat damage, an effect that causes the affected creature to fight another creature will still use its power to determine how much damage is dealt