Thank you for all of the suggestions, folks! Crusader looks like exactly what I'm after. Along with several other of the things mentioned.
Also, for those who mentioned Cave Story: That game may be the best thing to happen to Metroidvanias since... well, SotN!

It should be noted that Crusader has a control scheme that, while it does work on the keyboard, is a bit odd in its execution and might take some time to master. Be sure to check the subforum for a couple threads on the matter. Some folks struggle, others have no problem.