"an an" - " an an " -"air force" -antonov -chinese -vietnam -korean - useful for double "an"s, but watch out for things like "An Post" (excluded, but similar for other gaelic names). Usually just replace with an, but possibly other intentions ("and an", "at an", and "as an").
"was been" - " was been " - grammatically incorrect, but watch out for quotes and the song Lasterday I Was Been Bad. Possible corrections: was, has been, was being...
"in during" - " in during" often grammatically correct, but sometimes not...
"during in" - "during in" often incorrect but sometimes ok.
Prompted by a good question from User:SovalValtos I thought I'd investigate how to record discussions etc so you can find them. I knew it could be done, but wasn't sure how: the answer is at Help:Permanent link.
So here is my list to some discussions etc that I know are out there somewhere in Wikipedia but I'm damned if I can remember... The first example is not vanity - just my response to the question that prompted this list.