OK, for real: it really depends on my mood. I may seem very outspoken, or quite, or silly.
If we substitute 'could never do without' by 'would rather not do without' then my answer changes to: music, a subset of my friends, a computer, mangos, coffee, and love.
You are a drummer and can picture yourself playing in a dark indie/pop group.
You have a sufficiently weird & interesting video game in the making, and are looking for an artist/programmer/musician to join you.
You are looking for a concert buddy.