How many "brickwalls" have you broken down this week? I've now found parents on two different "brickwall" direct ancestors in the past 3 days. Neither required anything more than focusing in on what was already known and looking at sources that were available, online, and have been available since I became "stuck" on that ancestor. (The two people I have found parents for are John Thomas Lloyd and John Martin.)
I challenge you to take a new look at an ancestor you haven't worked on for awhile, because he/she is a bit more challenging then the others, and see if he/she is really as difficult to learn more about as you think. Write out on a blog post, in the research notes of the person in your genealogy program, in the "About Me" or a discussion post on their Geni profile, or even just a text document for yourself the steps you have taken to learn what you are trying to learn about this ancestor.
Think about what sources should have the information you are looking for. Have you looked at every available census record, birth record, marriage record, death record, obituary, will, newspaper article, cemetery, military record, posted "cousin bait" everywhere, checked for someone else who has done research at all the places online? Have you considered alternate spellings for names? Checked over the records themselves, in case they have been mis-transcribed?
I took a renewed interest in the two ancestors I discovered parents for (one of mine and one of my husbands) because of promising DNA leads, but you could also take the first "missing" ancestor (the first one that you don't have when doing an ancestor report like mine you can view here.)
An enormous amount of data is indexed and/or placed online everyday. The key piece you are missing on your ancestor may be waiting at Ancestry, FamilySearch, MyHeritage, Geni, Findagrave, Billiongraves or just about anywhere! (Not to mention what you could find if you went to an actual library or archives.)