I have a Samsung Impression and would love to have a WiFi connection w/o changing to a smartphone. Is a there a feature (no internet plan) phone with WiFi exist? if so, what model(s)
No there isn't. With any feature phone that the manufacturers put out with wi-fi, AT&T will have it disabled before they allow it on their network. You may be able to do this if you can find a non AT&T branded feature phone that has wi-fi and will run on AT&T's bands.
You can see if you can located a SE C905i or a used C905a that has been debranded. I believe the C905i will lack one of the US 3G frequencies, but if 3G service is not important to you, that may not matter. I believe Nokia may also make a few non-branded models that offer WiFi ability but are not classified as smartphones/QMDs by at&t.
=^..^= There must be a happy medium somewhere between being totally informed and blissfully unaware.
If you do some research on phones not sold by AT&T you can find a few feature phones that do have wifi. One that comes to mind is the Samsung Corby. There were/are several versions made. (I believe the Corby II was recently announced.) I considered buying one before I got my iPhone. Just make sure the phone will work on US frequencies. There was a Samsung Corby Pro, I think, that did have the correct frequencies, but it was difficult to find. Samsung had other phones with wifi, too, as did Nokia. Check phonearena.com and the phone company websites to see what is available now.