Take a set of CSV files with partially-overlapping columns and merge them by intelligently joining column headers.
For instance, say you have:
csvA.txt:
Date,A,B,C
2015-12-01,5,7,9
csvB.txt:
Date,B,C,D
2015-12-01,4,3,2
Running csv-join-columns csvA.txt csvB.txt will produce:
Date,A,B,C,D
2015-12-01,5,7,9,
2015-12-01,,4,3,2