What can/should I use on new iMac screen, everything I have tried leaves awful streaks...please HELP!

You haven't stated what you have used so we would take guesses. My suggestion would be to follow what Apple suggests in:

http://support.apple.com/kb/HT3226

specifically what they say is:

iMac

When cleaning the outside of your iMac, first shut down your iMac and unplug the power cord along with other connected devices. Then use a damp, soft, lint-free cloth to clean the computer’s exterior. Avoid getting moisture in any openings. Do not spray liquid directly on the computer. Do not use aerosol sprays, solvents, or abrasives that might damage the finish.

To clean the display on your iMac, first shut down your iMac and unplug the power cord along with other connected devices. Next, dampen the cloth that came with your iMac—or another clean, soft, lint-free cloth—with water only, and then wipe the screen. Do not spray liquid directly on the screen.

I Just use a microfiber cloth dampened with warm water, then really wrung out so,it is just damp.

Yes, initially it will look like it is leaving streaks, but it seems to dry fine.

My problem is static build up of minute traces of dust, lint and hair, from my Fiancées's cat, on my screen.

That's hard to just wipe off.