Data from retrosheet 2010-2013:
Walks will score slightly less than singles because they're not as evenly distributed. A pitcher is more likely to surrender a base on balls in safer situations--- when the baserunner will be less likely to score. Intentional walks even more so. I imagine some fraction of HBP are intentional as well, that may explain why they score ever so slightly less than a base hit, which is about as close to random as we'll probably get in this table.
Reached on Errors are not limited to single-base ROE, so that number is including some extra bases. Doubles and triples are especially high, and home runs are 100 percent obviously.
This is different, of course, from the percentage an event scores to lead off an inning which looks drastically different: