1. Pre-emptive burrowed banelings at the third base. A few builds either do or could have both burrow and banelings before the third is usually taken, and 3 or 4 evenly spread out banes could cover a whole mineral line (I think). Then just wait a minute or two for saturation or detonate immediately on the transfer.
2. Can you block gases from being taken with burrowed lings? You know, by burrowing them really tight up close to the geyser? I seem to remember something similar could be done in BW, and if it still works then I can imagine some trickery being possible with it (or if playing against Terran, at least a really cheap way to force a scan).
Thanks, and good luck!