Xenoblade Chronicles...it was so good I HAD to have a 2nd copy just in case. I got it when it had risen to $60 online...and as we all know it has since probably doubled in value from that price. Not that I plan on selling my 2nd copy.
Other games that I've technically bought twice:
Ocarina of Time
Star Fox 64
Super Mario 64
Donkey Kong Country Returns
Super Street Fighter IV
Pokemon
The Sims
The Sims 2
Not sure if VC games count but I've bought a lot of the old Nintendo "classics" more than once.
Oh, and it FEELS like I've bought New Super Mario Bros. four times...because it's basically the same game every time. #lazy
Upcoming Games To Get
Definite: Kirby Star Allies (Switch), Mario Tennis Aces (Switch), Fire Emblem (Switch), Yoshi (Switch), Pokemon (Switch), Kingdom Hearts 3 (PS4), Monster Hunter World (PS4)
Considering: Fe (Switch), Donkey Kong Country Tropical Freeze (Switch), The World Ends With You (Switch), Ys VIII (Switch), Street Fighter V: Arcade Edition (PS4), Kingdom Hearts 2.8 Remix (PS4), The Last Guardian (PS4), Shadow of the Colossus HD (PS4), Anthem (PS4), Shenmue 3 (PS4), WiLD (PS4)
Essay Pro