For bang-for-the-buck, it's tough to beat a $15 parakeet. I've had several, and my last one was the best. Left his cage open all the time, and when I walked in the door from work, he'd come find me and hang out with me for most of the evening. He had about a 25-phrase vocabulary ("Didja get the birdseed?" "Birds can't talk!" "I tawt I taw a putty tat!" Etc.), and was very friendly and approachable to strangers.
Biggest problem is that they don't live too long, even with carefully controlled diets and other precautions. My vet calls them "little tumor factories". Longest I've kept one is 8 years, but it's been 3-6 for the others.