Id say the most important ones to always have were Tovolar, Dire Overlord, Kessig Naturalist, and Arlinn, the Pack's Hope
Adrix and Nev, Twincasters Adrix and Nev, Twinscasters is another popular Merfolk commander, but this one certainly doesn't need you to be in a dedicated Merfolk deck
She never intended to lead the Alacrian Quickbeasts as the exemplar of her district, but after the tragic death of the original team captain mere weeks before the race, the mantle fell upon her shoulders
Suddenly, you have the run of the board from turn three onward with one of the best removal effects in the game: Armix gets around indestructible and theres no reason you wont have six or more artifacts on the field or in the grave at any time
Reality Acid Reality Acid has been used as a combo piece to nuke all kinds of permanents
It also takes the (dubious) honor of being the only card to mention grandfathers in its name