Univega: looks like a good solid bike. nice gearing range for pulling heavy things every once in a while. looks like everything is in good shape. would buy if proper fit
Trek: kinda pricey. old shifter/brakes (hereafter referred to as shakes) tend to gum up with age and might not have much life left, taller gearing, clipless pedals which you'd want to swap out at first
Centurion: ...interesting bike. a whole bunch of quirky things (most notably the weird headset locknut) that could come back to bite you. pricey too.
Technium: MONSTER gearing, fred-tastic flatbar conversion. Looks good besides that, but I think those two things kill it.
"tri" bike: impractical for nearly everything. including triathlons.
Diamondback: big gearing again, old shakes waiting to break on you, pricey, looks good otherwise.
Zebra: bucket of rust. makes me wonder what the hacksaw and rattlecans in the picture were used for.
In the end, I'd go with the Univega. It's fairly priced, and has good features for a commuter. The Trek, Centurion, Technium, and Diamondback are all decent second choices, but each has something a little off about them. I also wouldn't pay any more than 250 for any of them. Preferably $200, knowing that some of the older parts might need replacing right around the corner. Good picks overall.