Apps or tweaks mate?
And it all depends if you are a pirate, or actually support developers...
IntelliscreenX(Messages+) -7$- Adds Social feeds to the notification center, Messages+ adds SMS/iMessage quick reply options.
SBSettings -Free- Adds system toggles & drop down menu when activating said event.
Springtomize2 -3$- Adds just about every point of customization to your springboard, lockscreen, NC, and more.
Auxo -3$- Amps up iOS multitasking bar, adds application preview, adds system toggles, and more.
Activator -Free- Dependency with SBSettings, allows you to set an action with an event. Ex triple click home button locks device.
Winterboard -Free- Even though I think themes are bad and eat precious RAM, Ayecon is a secy theme, which costs 3$ I think.
Barrel -3$?- Makes moving Springboard pages that much more fun, youtube or test it out.
Callbar -3$?- Adds the banner style notification to calls, making everything a little more clean.
Favorite Contacts for the Notification Center -3$?- Adds your favorite contacts to the NC with a sexy tile UI
Instahancer -3$?- Adds a lot of functions to Instagram, save, zoom, copy&paste, etc
RunningList -Free- I use it to clear running applications by using the Spotlight page to clear apps.
TetherMe -3$?- Unlocks Apple's tethering feature, allowing you to tether your 3G/4G/LTE
I have so many more, but that's a short list.