Unmet Closing Conditions, Day of Close

How have people dealt with unmet closing conditions when you get to close date? Depending on the issue, I see a few primary options 1) close over the issue, if possible, and resolve later; 2) Delay close, which will cause a host of timing issues and incur additional costs 3) If really serious, walk away, which would be a terrible scenario

Night before close and morning of close can be very hectic and typically anything not resolved at that point has been minor in my experience so no real threat to closing but I am wondering if others have had more significant issues lingering and how that was handled.
Thanks!