Sometimes, mostly when either some console broke/got unavailable (I moved around the globe but couldn't take all my consoles with me) or rarely, if I got a game on PC and really needs a gamepad (or on consoles and could benefit from Mouse+Keyboard, but that only happened once yet). All in all, that's about 15 games total, not counting Super Mario Allstars and Super Mario Advance (aka SMB2; got both games as pack-ins)

With games I really love mostly. Collectors editions, goty editions etc. I will also buy digital titles and then pick up a physical copy at a later date and you can never have enough copy’s of retro games :D I have 4 copy’s of OOT in English and one in German for the N64.

If it is a good game I have no problem to buy it a second time, especially if it is a better version (higher resolution, better fps/frametimes, 4K textures, more or better effects/shaders...) or adds nice features (f.e. portability, convenience).But I don't buy two versions for the full price, the second has to be on sale.

I bought hundreds of classics digitally (GOG, Steam, PS store...) on sales although I still have the disc. And thanks to bundles and PS+ I have hundreds more modern games on different platforms.

Duplicate Steam keys from bundles I usually gift to Steam friends... the participants of the annual Secret Santa can vouch for that  

Of course I prefer it, if I get the second version (legally) for free... on Steam you get the remastered version often for free, if you bought the original (Skyrim, BioShock 1 & 2, Darksiders 1 + 2, The Vanishing of Ethan Carter, The Raven, The Whispered World...)

Cross-buy in the PS Store was also a great thing (while it lasted): one version optimized for the handheld and one version optimized for the faster home console hardware.

Today all Kickstarter backers of "Shantae: Half-Genie Hero" got a free Steam code for the Ultimate Edition (includes all DLC and other extras) additional to their chosen platform. Now I can play Shantae: Half-Genie Hero with all DLCs on my Vitas on the go and on my PC in 4K at home. All I payed back then was €11 and I got the main game + all DLCs (worth €40 to €55 depending on the platform) + backer exclusive content + the Ultimate Edition (probably around 30 bucks) on a second platform! And backers could play the main game and each DLC one week before the official release.

I recently bought the digital re-release of The Curse of Monkey Island.

Not really but I did rent Halo 2 a bout 30 times, and then I bought the legendary version with map packs.

You are just crazy, at least financially speaking.

I couldn't pay 60 bucks for a game once, let alone buying several times the same game.

You could buy other games with the money you spend buying the same game again. What you do makes no sense financially speaking. For your own good you shouldn't do it anymore.

EDIT: When I read some comments on this thread I come to the conclusion that some of you guys have a spending addiction.

For the love of God WHY?

I did buy some games twice when I stoped playing on PC. GTA IV bought on Steam, but never played, bought it again on PS3. The Witcher 3, bought on Steam on launch, but never finished, bought it again on PS4 and now Skyrim, Steam and PS4. Those are the ones I remember, but maybe there's more.

As long as we're not including remasters... GTA V and Rocket League are the only two I can think of.

I have GTA V on PS3+PS4+PC and Rocket League on PS4+PC.

One day I sold a lot of Gamecube and N64 games. That was a big mistake and i will never do this again, ever. So I rebuy these games occasionaly, the latest addition was Luigi's Mansion. I still need Starfox Adventures, Smash 64, and a couple of others.