I was going to say someone engaging, enthusiastic, not full of themselves...
You look for someone you can work with and will work well with the team. I know HR types will squeal, but to get to interview every candidate should be able to do the job - not every candidate will work well with the rest of the team.
"what sets you apart from the competition?"
Bullshit question - will be followed up by bullshit answers.
Nothing is a greater turn off at interview than an over confident, arrogant, bullshitter.
I look for someone who can think through complex problems under pressure - and quite often pose work related scenarios to see how people cope with them...
... and very often the ones who breeze through such technical scenarios are not the ones that capture your attention. The correct, off by heart answers might demonstrate suitable specialist knowledge, but the candidates that sweat it out, out of their comfort zone, and still think through a coherent logical approach, even if the answer is ultimately wrong... are the ones that I like to draw out. Even though they know they are struggling - what they are actually demonstrating is ability to think laterally and to remain cool under pressure (and close scrutiny).