Speaking of big creatures, if you are the rare green deck that doesn't have any, Khalni Ambush drops from great to medium or even bad, but since big creatures are more or less green's thing, it's hard to imagine too many green decks that won't get value out of the instant-speed fight spell
When it comes to Tinker I like at least two good targets, ideally somewhat standalone ones
Mirko, Obsessive Theorist lets you return a creature from your graveyard to the battlefield, so long as that creature's power is less than Mirko's
Learn More Custom MTG Proxies that shuffle like the real thing Want to test a new brew, tune your lines, or play Commander without taking out a second mortgage for your manabase
Tap: Add R or W
At the beginning of your upkeep, return target creature card from your graveyard to the battlefield