Being able to prevent damage to your creatures is good, and its even better when your commander has mana sinks built into them
This is especially true for commander cube if you support dragons as they're making a bunch of dragons that are not red, adding more density to enable the 5c dragon deck that I keep trying to make a reality
For just three mana and sacrificing an artifact, Tinker lets you tutor any artifact in your deck directly onto the battlefield, which allows for things like a Turn 1 Blightsteel Colossus or God-Pharaoh's Statue or Bolas's Citadel, all of which are pretty close to unbeatable
Ain't no spotlight in town that ain't eyein' Kitt, and she dang glows in 'em
In Giselas case, thats double damage for any source damaging opponents or their permanents, and incoming sources of damage halving, rounded up