What Extras do you like?

Ive started this topic because after playing Mafia 2 which is a great game but has limited replay value, so collecting the playboy mags, wanted posters and getting achievments is what's keeping me playing it for now, that and the epic shootouts in missions like The Buzzsaw and Room Service.
 
I was wondering what extras do you like to see in games, specifically single player, is it concept art, different costumes, challenge levels etc? and which game/s do you think have done it right?

The only time I'll replay a game is if it'll be significantly different like playing Fallout 3 with different decisions.

I like alternate costumes, but on the same token I hate unlocking crap so I am kind of at a crossroad as far as that's concerned.  The most appealing thing to me, at least for single-player is being able to play the main campaign again with a different character.  I think Ninja Gaiden did that in one of its numerous variations.  Maybe it wouldn't make sense storywise, but since it's your second (or later) play-through that shouldn't be a huge consideration.  It'd probably take a lot of work though in some situation for the game developer, so it's not feasible for every type of game. 

New Game Plus.
 
Let me play the game again over again super-powered, I don't care if it makes the game broken. I love games like Shadow Complex or RE 5 that let you play again with things carried over. It also encourages playing again on higher difficulty levels.

New Game +
Also things like Bioshocks audio diaries!

Bonus levels are the best incentive to keep playing, but they take a long time to make in comparison to concept art and collectibles. Costumes are also good, especially if they're ridiculous like Uncharted and Uncharted 2's "Doughnut Drake."

Resident Evil 5 is the clear example that everyone should follow.

Depends on the game, 
RPGs give me a New Game+  (Tales of Vesperia)
Fighters give me TONS of unlockable costume stuff (Tekken 6) 
Racing Games give me TONS of cars to buy and upgrade (Forza) 
Sandbox Games give me TONS of collectibles ( Just Cause 2) 
FPS give me an online leveling System that actually determines the caliber of player I face (Battlefield MC: 2) 
Platformers give me...... I don't know, Do platformers have replay value? 

" How abouuut. Crazy ass wannabe pornographic dance video at the end of Bayonetta? That is one of the best from a 360 game.  "

Here it is:
 

Commentary.

Commentary. Like Valve games and Super Monkey Island 2 SE did.
Costumes
New Game +
Bonus Game modes that are unlocked after beating the game or entering a code.

My favorite collectibles in a game is definitely the dog tags in MGS2. Dog tags for nearly every enemy on every difficulty level. You had to change up your strategy multiple times, and approach enemies in often unique ways to obtain the dog tags. Especially on the harder difficulties.
 
So in general, I like any collectible that are actually interesting to get, seeing as I am a completionist. Rather than just the usual "boringly look at every nook and cranny for collectibles". If these collectibles unlock anything, that is an extra bonus, but I like to get them just to....get them all.
 
Besides that, I like stuff such as new weapons, costumes, skins, New Game +. Anything that might make the 2nd or 3rd playthrough more enjoyable.

Collectibles, though not hidden like a needles in haystacks like those bleedin' pigeons in GTAIV -_-. Unlockable costumes I always love to have rooting for. Weapons, and if the games a little on the arcade side, some extra characters too. Or at least character skins to add some improvised comedy like in the Uncharted series. Basically Saints Row 2 is the definition of what I want in the way of unlockables <3

Toss up between the episode with Patrick Stewart or Daniel Radcliffe. I love Extras and love how Ricky Gervais doesn't run his shows into the ground just 2 seasons and an hour long special to wrap them up.

" @carlthenimrod:  Yeah I loved Ratchet and Clank for that, technically the difficulty level goes up after your first playthrough but it didn't feel like it due to the upgraded weapons and armour. "

" Platformers give me...... I don't know, Do platformers have replay value?  "

For some reason, this thread makes me wanna play more of Ratchet And Clank: A Crack in Time

"How abouuut. Crazy ass wannabe pornographic dance video at the end of Bayonetta? That is one of the best from a 360 game.  "

I love games that let my bring my goods/gained abilities to the next difficulty level like Devil May Cry.

unlock ables to make the game replayable. resident evil 4 and 5 are great examples of it. it was pretty short game but make them a little bit longer. i enjoyed playing that game over and over. i think i beat it like 4 times. 
 
i also enjoy different endings and clips of developers making the game or talking about the game.

i will never replay a game, i am some kind of adventure-seeker

" Here it is:
 

Commentary.

"