My favourite aesthetic armour is the Daedric set for heavy, and the Light Chitin set for light. In terms of practicality, the Daedric armour is still the best, but I usually stick with Ebony in the end game, smithing it up so it's even better than Daedric. However, if we're talking about mixing and matching, I really like the steel plate gauntlets and boots, combined with a full fur chest and dawnguard full helm. Just looks cool to me.
For mages, the Archmage robes or Expert/Master robes with circlets. This combination looks very cool.
For heavy armored warriors: Steel plate armor set with the Dawnguard heavy helmet.
For light armored warriors: Scaled armor set with a circlet. There is a mod that allows you to create and improve Scaled Horn armors. Amazing.
Just to mention the least favorite: Elven armor