Assassin's Creed and Red Dead Redemption's horse riding are nice. Thief for stealth. Dark Messiah for combat, magic (freezing enemies, freezing the floor, setting environment on fire with fireball and stuff like that) and a less overpowered kick ability (it should still be possible to kick people from cliffs if they are standing near the edge). Though I think mostly the animations and the feel of the combat should be Dark messiah like, the damage should be determined by your skills and maybe stuff like the momentum/speed of your weapon (like in Mount & Blade).
Assassin's Creed and Mirror's Edge for acrobatics (if you have a really high acrobatics skill) and maybe Brink's SMART system could work.
The Witcher for it's darker atmosphere (you might even look at the S.T.A.L.K.E.R. games for inspiration, though these are off course far less similar to The Elder Scrolls than the Witcher is).
Assassin's Creed and Mirror's Edge for acrobatics (if you have a really high acrobatics skill) and maybe Brink's SMART system could work.
The Witcher for it's darker atmosphere (you might even look at the S.T.A.L.K.E.R. games for inspiration, though these are off course far less similar to The Elder Scrolls than the Witcher is).
Aaaah yes the horse riding. True enough, though I think thats more about doing what they already do better. Same with the Thief part.