Rocksmith (on Steam, but I believe there's a console port too, if you're into that kind of thing).
[Game synopsis, if you're not aware:]
Spoiler
Basically it's like Guitar Hero, except you plug in your real guitar (any guitar, using a 1/4"-to-USB cable) and actually learn how to play it. Note complexity scales to your ability level, so newbies can just play one important note from a phrase, and at its top level you'll be properly playing the song. You can also play bass, either by plugging in a bass guitar or having the game emulate bass sound from your lead guitar. And finally, you can use the game as an amp - there are tons of emulated effects pedals that you can fiddle around with. The pedals are unlocked by performance in game, which provides the sense of progression.
After several years of periodically messing around aimlessly on the guitar, running through the same little selection of songs I only knew the chords to but not any sense of rhythm, I hadn't really made any progress. A few weeks playing this game between 40 mins to 4 hours every day, and I'm
finally making some serious improvements, and can do things I couldn't imagine ever being able to do beforehand.
Unless you manage to find a really good guitar teacher (I haven't had such luck), this is probably the best learning tool out there. It's very fun, and scales nicely to ability levels. I wouldn't recommend it for starting from scratch, because you'll need a real person to teach you the most basic techniques, but Rocksmith is ideal for mastering those techniques, learning a few more advanced ones and nailing down your muscle memory.
The most important thing for me is, unlike every other avenue I've tried, I
want to keep learning with this - it's not a chore. It's well made, highly enjoyable and more than a little satisfying. And like Rock Band, it's made me fall in love with music all over again. /cheese.
Unfortunately I've just snapped my guitar strap, so I'm stuck with my ham-fisted lap-playing ability until the new one arrives.