6. Quarians
Essentially Bioware's take on Eastern religion - interaction with the more strict Quarian race gave ME2 one of its best scenes, where no matter if you were romantically involved with Tali or not, bargaining with the clan leaders and sticking up for her place in the fleet was brilliant. Not only that, but they form one half of a very enticing narrative coin, having designed the A.I. Geth race to benefit their colony only for them to gain sentience and rebel - giving you great choices in Mass Effect's 2 and 3 where you sided with either the creator or subject in relation to the very idea of creating life. Being tech specialists, for the most part people took Tali with them due to her long-range drone and hacking abilities, but factoring in that each new planet you'd explore in ME4's gigantic open-world would mean recalibrating your suit to best effect, the possibilities for customisation and upgrades either on or away from the Migrant Fleet are endless.