I've played bass the past 11 years. Played sax from 5th grade through high school switching to bari-sax the last 3 years. I'm in a band now playing bass and it's pretty fun. We rarely play money making gigs, but we're planning to record soon. Hopefully that will end well. I'd definitely recommend learning something. Anything is better than nothing. It's a creative outlet, an interesting hobby, and it makes making friends easier.
If you want to have a solid musical foundation that will aid you in almost all musical endeavors, then learn piano. It's great for songwriting, accompaniment, arrangement/composition, and a good pianist is invaluable when you need one. Knowing piano will also help you learn other instruments easily. All the exceptionally talented musicians I've met have started on piano or use it as their main musical tool. Also, pianists(especially jazz pianists) are infinitely sexier than guitarists, but don't try to look cool playing keys in a rock band. It just doesn't work. Keyboards are pretty cheap nowadays, so the entry cost is pretty low.
If you just want to be able to play a song relatively quickly, learn guitar. It's pretty easy to sound ok, moderately difficult to sound good, but pretty hard to sound masterful. People tend to pick apart your playing more than they would other instruments. even non-musicians do it. Entry cost is low.
Bass is a great thing. As a bass player you are the marriage between rhythm and melody. You hold the band together and have a significant influence on the "feel" of the music in an indirect way. People listening will rarely notice you, but will feel it missing and notice when you fuck up. In some ways you're more playing for your band than you are the audience. Bass is easy to pick up, but it's hard to find genuinely good bassists. If you can keep the groove in the pocket and have a good understanding of chords, you'll never be without people to play with. If you can sing backup vocals as well, other musicians will do depraved things to get you in their bands. DISCLAIMER: Chicks will never dig you for your bass playing. If a chick digs you it will be because she genuinely likes you and/or likes that you're in a band, but never because you play bass. Entry cost is low.
Good drummers are always in need and drums are easy to find joy in. you're hitting things to make music, so it's visceral and creative which is a rewarding combination. The entry cost is high; you won't find a kit worth playing under $500 unless you're really lucky. Maintenance is also something to consider(heads, cymbals, and stands break). Don't bother picking up unless you have naturally good rhythm and/or serious dedication.
Whatever you decide to play make sure approaching it in the right way. Make sure you're playing because you want to make music and that the instrument you're using is the way you want to do so. Don't waste the time and money to learn an instrument if you're not enjoying the challenge of learning it.