Creatures and Artifacts with activated abilities for the general to use
Untap self abilities (like Horseshoe Crab), again for the general to use. Cards that refer to themself do work properly with Mairsil (the name gets replaced with "Mairsil").
Clones act as extra ETB effects for Mairsil (you clone the general and just let the clone die)
Sakashima and Quicksilver Elemental are basically more copies of the general
Click here for a text version of this decklist
Click here for my EDH Commander decks