NCSettings on my iPhone, plus a few other tweaks (can't remember what it's called, but the one where you swipe across the keyboard to move the cursor). I'm a themer, so Winterboard will go on, though am pretty sure none of the themes will work right on an iPhone 5 out of the gate, so I'll probably have to wait for theme updates. I'll also install Springtomize and Iconoclasm, but those will also likely require iPhone 5 updates, and I'm not sure how many JB apps/tweaks will be ready quickly. Also, I'll install Nitrous to give my 3rd party browsers access to the native Nitro engine.
On my iPad Mini, I'll be having a lot of fun exploring all the iPad JB tweaks, which should work pretty quickly out of the gate, I'd imagine...but I've never had a jailbroken iPad, so I'm excited for some of the possibilities there.