Corns, hands down, for all the reasons listed above. However, that doesn't mean lots of others aren't almost as good, so if someone doesn't 'like' corns, there are other choices. For example, next on my list would be california kingsnakes (better than other kings only because they're so readily available). Some tricolour milks/kings are really great choices as well. North American rat snakes would be great, though they're starting to get a little bigger in some cases. Same with Pituophis, plus temperment tends to be more of an issue with them, in my experience.
Thamnophis and Nerodia are great (I've got lots), but their long term captive care is considerably more difficult than most of those listed above.
Babies of anything are often more nervous (therefore more prone to biting), and generally, less hardy than well started juveniles, so for a first snake, I'd say don't get a brand new hatchling!
I'll concur with Marisa, though, that balls are less effort if you know what you're doing and are properly set up. But since there's more to know, more to set up, and they're far more finicky on average, I still wouldn't recommend them for beginners. Besides, who wants beginners to do less work? They should be enthusiastic about their first herp, and WANT to do all of the things required to keep it:-) Less work shouldn't be an issue until at least the sixth!!!