Snark Tight All Instrument Tuner
I like the Korg products also, but this little guy is perfect to attach to your guitar. It's especially useful when playing a gig. I can easily check my tuning in seconds without having to take the time to search for it since it's always attached near the tuning pegs.
If you have trouble remembering to turn battery driven products off, this one has an automatic shutoff after 2 minutes. It's great for both bass and guitar and has a capo transposition feature for guitars.
I like the fact that it is sensitive enough to keep my bass in tune while being easily in reach to utilize during a gig. If you want to keep your bass in tune and not worry about battery drain, this is the answer.