That’s one option for different sounds.

We’re creatures of habit, and all have our favorites. When you’re inspired, you reach for your “favorite” instrument. You have your “favorite” set up, strings, tone, etc.. But what about those times when your “favorite” just isn’t working? Say, you’re auditioning for the bass spot in a funk band, and your pick technique isn’t what the music needs or wants. Or, you want to just broaden your horizons and try something new, because your “favorites” just aren’t doing it for your right now.
Here are some options to consider:
Fingers/Pick: The two most commonly used options, for sure. However, the large majority of musicians fall into a “I primarily use _____” or “I only use _____” camp. So, if you’re a fan of the fingers, grab a pick and give it a go. If you’re more of the pick-weilding type, consider using just the fingers. The tonal differences between the two alone merit learning – and appreciating – both main options.
Funk Fingers: A long time ago, history was made (or recorded) when drummer Ray Bauduc started drumming on the strings of Bob Haggart’s double bass, for “Big Noise from Winnetka.” This sound was percussive, moreso than the norm. Decades later, Tony Levin would strap drum sticks onto his fingers for an equally percussive option on his Stingray. While the former is forever engrained in jazz history, the latter is commonly known as Funk Fingers.

While it doesn’t necessarily have the style and impact that watching a drummer banging away on a bassists’ axe has, it does achieve the same result. And thankfully due to a licensing agreement with Levin, you can buy Funk Fingers from Expanding Hands Music.
Bow: Using a bow on your instrument is a very old tradition, but isn’t readily thought of for electric guitars and basses. People may have dabbled with it, but the lack of a heavily radiused fretboard makes it rather difficult. However, things like that don’t stifle the truly creative artists.

There are lots of things to consider with this. First, you need a bow and like any piece of musical equipment, they can get expensive very quickly. Second, you need rosin to help the bow hair grip the string, which can make a mess that isn’t easily removable. That said, a cheap fiberglass violin bow and some rosin should be easy enough to at least give a try, if you’ve got the time.
For those that want something a little different (and I do mean little), Expanding Hands Music has also released the Finger Bow, which is a 12″ long bow that can be attached to the ring finger, allowing you to play arco and pizz quickly and easily.
eBow: If you don’t want to deal with the hassle and mess of an actual bow, you can try out the eBow. Using an electric wave to generate sound, you can make lyrical passages very similar to a bow. Biggest plus is that you don’t have to have a radiused fretboard to be able to pick just one string, like a traditional bow.

There are countless musicians that utilize this invention, bass and guitar, and is fairly easy to get ahold of, if you’re in the mood to try it.
These are just a couple of the more common options that you can use/abuse to open up the tonal possibilites of your instrument, and give your right hand something new to learn. For those that have tried any of the above, how did it work out for you? Any considerations or issues you had?