I am the one that brings the weirdness.. I also bring the professional element.. I also am the glue between the guitars and drums and extra voicing for the vocal melody. I am the mediator the counsellor and the most down to earth. I wish I was the most talented but alas not to be.
Bass players are natural leaders, IMHO. We're not the lead singer or front man, we don't get the lead breaks or the drum solos... Nope, not in the spotlight but I'll be damned if we're not missed when we're not there.
And everyone on the dance floor is there because of us and moving to what we're producing.
What I also find interesting is the "political" nature of the role - the moderator, peace-keeper, glue, etc. relative to keeping the band whole... Very cool...
Since some replies have a serious side, I'll add that in addition to my "anchor and engine" role, I drive the song selection, chart all the music, coordinate and run all the rehearsals, song arrangements, stage direction (starts, stops and re-directs on the fly)... Ok, I'm a bit of a control freak...
Oh yeah, and play bass, run the drum machine (not for long!) and sing back-up...
I am the perfect storm of musical theory knowledge and gear geekery. I am the one that the fugly girls talk to after the gig. I am the one making your chair vibrate. I am the one who laughs at my own on-stage banter. I am the one who has rehearsals every day for six hours AFTER my nine-to-five. I am the snappy dresser.
I'm the one that doesn't drink, but enjoys it when the others get hammered. I go with the flow, and know how to have a good time. I'm there to have fun, so I don't let little things like missed notes, missed beats and missed lyrics get in the way.
We have a blast, put on a good show and I don't think there's ever been a fight about anything in the 5 years that I've been in the band.
I'm the disciplinarian. When someone messes up, they immediately look toward me in horror to see if I noticed. Of course, I'm already looking at them...
When I mess up, it's improvisation... Usually it works like a charm.
In the band I play guitar, sing backup, and the singer and I write most of the songs together.
I record demos at my home studio.. in that environment I'm the engineer, drum machine programmer, keyboard player, bass player, guitarist, lead vocal scratch-track performer, backing vocals, composer, and Designated Button Pusher.