Sometimes I feel that it is easier for me to tell others which airguns I would NOT recommend, than to actually recommend some! I think that the approach stated
JimNM above is a very good one. But people are all so different. Will the hook be set in them like it was in me, to take up airgun shooting pretty seriously? Or will they maybe find out that they have other things they like doing better, and the airgun sits in the safe? So do you have them take the 'buy once, cry once' approach to a higher end gun, or recommend something in a much lower price range which, if it doesn't work well (poor trigger, hard cocking, etc.) might put them off to airguns in general?
I have actually purchased less expensive airguns in the past - not from Walmart or Big 5, but guns like the AV Avenger, Benjamin Cayden and a Beeman. Just so that I could try them out and see if I could recommend them. In one case it was a big YES, in another it was a "not so much," and with one it was "don't do it!"
I am fortunate in that I have a somewhat variable range of guns in my collection, and a shooting area in my back yard. So I can let folks try some stuff out and see what works for them. And it doesn't stop with the gun either - preferences vary widely regarding the optics too.
After they have shot certain guns, I then can sometimes give them sites to look at for reviews. Steve Scially at AEAC is one of my favorite sites to recommend - His high standards and high ethics show throughout his work. He shoots guns from a wide variety of price points, his presentations are clear and educational, and his work is entertaining, at least to me.