If you included modded companions, Inigo would be at a tier above the top tier. The vanilla companions are absolute trash by comparison. They don't even do everything an NPC can do in the game; but Inigo does. Can literally comment on any item you see or touch, interact with other NPCs, has a schedule he follows when not actively following you, follows his wants and needs... The dude who made him went all out with it and puts the actual developers to shame, since most of these features are simple check boxes in the editor.