Do you have any games you've bought multiple times? I'm not talking about the "It's been bundled twice so I have a Desura and a Steam version" or even a "I have a DRM free and a Steam version from a bundle" here. I'm talking about games that you've explicitly purchased more than once.

Crazy enough, my top one is Torchlight. I've got 4 different versions of Torchlight.

I loved the demo when they first released it, so I bought it from the Runic website. I didn't use windows at the time, and was having a devil of time with the sound in WINE. I played half the game with no sound, then I read somewhere that the Steam version worked better in WINE than the Runic version, so I bought it on sale one day (incidentally, it was my first Steam purchase). Then there was the Humble Bundle with a Linux version, so that was an insta-buy. And then, GOG offered it for free at one point, which isn't really a buy, but I acquired it too.

Baldur's Gate 1 & 2, and Icewind Dale have all been purchased three times. I have the original CD's, a GOG version, and the Enhanced Editions of all three of those.

I have Planescape Torment, Thief: The Dark Project and Deus Ex on CD and on GOG.

I have Age of Empires II on CD and the HD version on Steam.

GTA3 I have twice on CD, once by itself, and once as part of a pack that included Vice City and San Andreas as well.

What games have liked enough to purchase more than once?

FO and FO2.

I was given a two-game jewel case edition by a friend. Later on, I picked up a 2nd FO disc at a thrift shop, concerned about scratches.

Then I picked up the GOG versions.

Similarly, I had physical copies of Fahrenheit and Baldur's Gate and VTMB and TOEE, and I got digital copies of all those.

Couldn't even begin to list them, probably at least 50% of my games are duplicated (physical and back up digi) my other games are mostly console stuff, some of which I replicate on Steam as well, if theres a big discount eg. Saints Row Franchise for a tenner etc.

I have Assassin's Creed twice, one retail, one GOG.
Same with the Runaway series, got them retail and on GOG as well.
I have a retail copy of Dragon Age Origins, and I bought the Ultimate Edition digitally when it was dirt cheap. It was much cheaper than buying Awakening and the DLCs seperately :P

crossword puzzles on the back of cereal boxes... prob...

Yep. I own the first four Blackwell games on GOG, Steam and Humble. I think they are great games that deserve some support, and since I got them on sale the first time around, I didn't mind paying for them again to reward the creators.

I'll probably also purchase the KOTOR games now that they're here at some point, even though I own the retail versions. These games are really good, and I'm willing to throw some more money at them for DRM free versions when I have the funds.

EDIT: Oh yes, I also own Gray Matter twice. I bought the GOG version when it was released, and liked it so much I purchased the collector's edition from Germany as well.

Triple Skyrim here,

Skyrim (2011 Release - Preordered) - Boxed
Skyrim - Legendary Edition - Boxed
Elder Scrolls Anthology (All other TES games came with it so I have double of those too except Arena and Daggerfall)

I have Syberia and Syberia II from a gaming magazine as gifts in CD form, but I missed them from my Steam library so I bought them there too. :)

I had the DOS and SNES versions of Simcity.

Also I had the original Warcraft 2 and Warcraft 2: Tides of Darkness CDs, along with two copies of the Warcraft 2 Battle.net edition for some reason.

Also I have the original Age of Empires and Age of Empires 2, but bought the collection that included 1 and 2 and their expansions. All physical copies.

Civ 4, I have the original and the complete edition.

That should cover it, I hope.

I have some duplicates, but none as much as the Ultimas. Starting from the old days I have Ultima Trilogy I-II-III, and Ultima V for the Commodore 64.

Much later, but still before I could even dream that these things would come back for sale, I bought second hand some EA Compilation CD that looks like it was originally bundled with some Creative product. It has a few of titles of some interest, but I got it for Ultima VII Black Gate, Ultima Underworld and Ultima Worlds of Adventure: The Savage Empire.

Since it didn't include Serpent Isle nor the expansions for Ultima VII, I later got me The Complete Ultima VII, which was a perfect set to go with Exult at the time. Similarly after finishing Ultima Underworld I wanted to play Ultima Underworld II, so I got me a nice I & II compilation set. Then a boxed edition of Martian Dreams on 5¼-inch floppies to follow Savage Empire. And then I got the Dragon Edition of Ultima IX, with its included Ultima Collection, Ultimas I-VIII once more.

I thought it would stop there, but finally, last christmas sale I grabbed all the Ultimas here once more, figuring they at least come with nice scanned manuals.

I think I have a lot of C&C multiples because they did a horrible job of managing their box sets. XD I think I have three copies of Tiberium Dawn from 3 different sets, each of which only shared one common game, Tiberium Dawn.

I started counting the games in my GOG library I already have at least one CD-ROM copy of or had deliberately bought from other stores before. I got to 30 games before I got too tired of counting anymore. =/ Needless to say, it is definitely way more than that number.

I forgot about Assassin's Creed. I have it on XBox and GOG.

A lot but I don't entirely remember because I get rid of my physical versions when I get a digital unless its a physical collector's edition.

I still own Halo for PC and the original Xbox.