Let's do some tidying up e.g. JDBC
Yes, I know it's more fun to add sexy new features and pursue the cutting edge aspects, but lets consider cleaning up some of the uglies that we've been living with so long we no longer imagine them being straighted out.
JDBC carries minor but oft-encountered irritants, for example. Like why on Earth does it not use java.util.Date for it's times and dates? Who decided we needed a java.sql.Date? (thus resulting in many classes which have to use two different classes called Date) Like the (lack of) proper BLOB/CLOB handling, the current system seems to have been written by someone who didn't quite grasp how LOBs work.
Yes, I know straighening out these things would be a pain, because of all the third-party implementations involved.