Mount and Blade series (as a note, it becomes infinitely more fun when you RP as someone from Westeros)
Orcs Must Die
Neverwinter Nights 2
Medieval 2: Total War
Assassin's Creed series
Legend of Zelda series
Ace of Spades
Gold Version (plus the rest of the series, but Gold is the best in my highly nostalgic opinion)
Honorable mentions go to Bastion and KOTOR since I actually beat them. SW Battlefront 2 gets one because I played it forever.
I have yet to play Skyrim, New Vegas, Baldur's Gate, or actually finish half the games on this list.