I like the difficult choice of which opponent gets the counters, especially if you have a way to remove the opposing creature after you put the counters on it
On the other end of our rankings, we have Saskia the Unyielding, who is is pretty much just a creature that attacks and blocks
A 1/1 flier is also way more useful than either a 1/2 or 1/3 body on the ground and so Thopter Engineer is a much more rounded and independently playable card
Edge of Eternities The play booster packs of Edge of Eternities contain some spectacular art
It takes just three turn cycles to trigger this in Commander, assuming you dont add counters, so you have the time and mana to set up leaves the graveyard synergies or similar effects
Sadly, nearly every other answer costs some amount of mana, so you can expect to be slowed down due to them