Demos you played multiple

...times. Damn, I got the title wrong! -_-'
 
The majority of games seem to have some kind of a demo or trial version, and I wanted to ask you guys which demos you enjoyed the most and replayed multiple times. 
 
Or it's just me who plays a demo more than once ;)
 
(Also multiplayer betas kinda don't count, keep it singleplayer only please).
 
For me it's:
 
Burnout Paradise Just so much stuff to do in that demo. I played it a few times a day for almost a week and couldn't get enough. Weirdly enough I never bought the actual game.
 
inFamous A chunk of inFamous' open world was enough to have me sitting in front of my PS3 for a few evenings. I loved how there was such a variety of ways a mission could be played out. Bought the game (almost) day one.
 
Uncharted:Drake's Fortune Similar to inFamous I loved how different encounters could be played in various ways; climb a ledge here, flank there, etc. Day one purchase as well.

Burnout Revenge jumps immediately to mind.

mortal kombat

Shareware version of Duke Nukem 2, every single one during the PS1 era.

Memorized all the lines of dialogue in a Ratchet & Clank 1 demo, Tales of Vesperia, Bayonetta and Bulletstorm more recently.

In recent years: Crackdown, inFamous 2, and Saints Row

Just Cause 2

Just Cause 2, I played that a lot.

Played the Wheelman demo over and over again, because that car chase was so much damn fun. Still haven't played the full game yet, though.

More recently, I played the Red Faction Armageddon demo several times to experiment with killing and destroying in different ways. I remember playing the Guerrilla demo a bunch of times for the same reason.

Even more recently, the DNF demo because it's Duke Nukem.

I think the Battlefield 1942 demo was my most played demo. That demo was just too awesome for it's own good.

I bought 7 or 8 Ultima Online: Renaissance discs for $10 so I can keep making new accounts and playing for 30 days. That's kinda of similar to a demo, except for the part where you pay for it.

Mortal KOMBAT!

Just Cause 2, Red Faction: Guerrilla, Bulletstorm, both Crackdowns (2nd one just because you could glitch it to last, and it was really fun to dick around with someone else, Backbreaker, InFamous, both Uncharted games, Cargo and probably a ton more that I can't really think of.

Populous: The Beginning.

Tony Hawk's Pro Skater 2.

MGS

Just Cause 2

Burnout Paradise, because I just couldn't decide whether I wanted to buy the game or not.

Crysis, because I was so ridiculously excited for that game.

Mortal Kombat, because I still haven't bought it, and I want to play it everytime I see someone play it...

And a whole lot more...

Saints Row demo because it was basically the first open world, GTA like, next-gen game at the time.

Batman: Arkham asylum, best demo ever...

Dragon Age II, it was pretty cool. Not sure I should buy the actual game though.

Just Cause 2, Dead or Alive 4, Ninja Gaiden Sigma, and just about anything on a demo disc in my possession last generation and before. 

Anything and everything that was on that demo disc for the original PS1 on day 1. Toshinden and whatnot.

Battlefield 1942...was practically a free game in retrospect.

Skate...i played a lot of that over and over when it first cameout.

Batman: Arkham asylum, best demo ever...

Burnout Paradise, Batman: Arkham Asylum, Crackdown 1.
 
I never bought any of these games though

Bad Company 2 multiplayer demo, Saint's Row, and Dead Rising.

Crackdown... agility orbs
 
B:AA
 
Jus' cause

I played the Mortal Kombat demo on my PS3 about 3-4 times before my PS3 died a few weeks ago. Every time I wanted to go buy it I would play the demo to remind myself I don't like fighting games.

Pretty much every demo I've ever played that wasn't total shit.

World of Warcraft
Left 4 Dead 2

Mafia 2, three times at least. Then i found out how you could disable the demo timer. And pretty much explored the entire demo area, loved it.

I don't like demos anymore because I don't like waiting for them.
awww good ol' OPM days every month like 10 demos on a disc.

The most recent ones have been BioShock and Just Cause 2.

Batman:AA, because it's awesome.
Bulletstorm, because I loved the skillshots and replayability, love the actual game but haven't replayed it too much (this year is busy for games!)
Killzone 2/3, because I wasn't sure about getting either (eventually got both and found them to be alright, but they got traded in all the same)
Mortal Kombat, played it with every character on every difficulty, but weirdly enough I never brought the game due to Portal 2.
Basically, I replay demos of games I am seriously considering buying, to stretch them to their limit - I mean hey, if a demo can entertain me for ages, the game will multiply that!
 
Edit: Weird, I can't un-bold the Mortal Kombat line, and didn't click bold to begin with!

Just Cause 2. Especially cause you could glitch it so the timer wouldn't end. Pretty much as good as the actual game at that point.

Just Cause 2, Red Faction: Guerrilla and  Batman: Arkham Asylum

Played Left 4 Dead a lot before it came out.
 
Superman Returns, no idea why but I thought it was great but I never got the game.
 
Batman: Arkham Asylum and Just Cause 2 I put a good few hours into before they came out and I got them.
 
And of course I played that PS1 demo collection that came with the console so many times (Medievil and Tekken 3 etc.)

Burnout Paradise, skate, and Just Cause 2 come to mind.

L4D .. the original, me and three other mates went rhough that until after the game came out, was only two levels and we musta went through them 500 times

Jazz Jackrabbit 2 shareware, the first Ratchet and clank. More recently Just Cause 2, Arkham Asylum and bulletstorm.

mortal kombat

I played the Bioshock demo over and over and so I bought the game and still have not gotten past the end of the demo part of Bioshock.

Halo Wars, me and my my friends played that demo almost everyday until the actual game was released.

Zone of the Ender 2

I bought a magazine that packed in with the Demo, and that was the only time I ever bought a gaming magazine in my life. Well worth it, played it over and OVER again...and I even tape a section to the VCR lol

gona dig up that tape...and the VCR aswell

Heroes of Might and Magic III 
Skate

Just Cause 2. The demo for this game was a really good introduction to the craziness of the actual game, though I'm fairly certain I never actually played it until time ran out at any point. I played it until I grew tired of the madness I was causing and then turned it off, but if I ever felt that I needed more time there was a glitch to disable the timer, wasn't there? Still, the demo gave a brilliant impression of the overall game.  
Brutal Legend . The demo for Brutal Legend was brilliant as it was the first level of the entire game, and I enjoyed it a lot. I played it a number of times before actually buying the game and discovering that the demo gave a better impression of the experience than the actual game did. Had the game been like the demo then I reckon that Brutal Legend would have been a better overall game. 
Crash Time . This refers to all the demos. I have no idea why but I enjoyed all of the Crash Time demos and I'm seriously interested in buying the games thanks to my experiences with the demos. Strange considering I don't remember the games ever receiving positive reviews anywhere except Germany, but they remind me of the earlier Burnout titles and are an absolute blast to play.