For travelling knitting, I always add in several balls of dishcloth cotton. If I finish the other project(s), or run into any problems, I can always knit dishcloths with no pattern. Since I never have enough of them to supply all my family/friends that want them, it's just a nice thing to have along.
My last knitting emergency was removing an afghan from its ziplock bag and discovering that the point protectors on the needle tips had come off. Dozens of unattached live stitches were just waiting to unravel. Since it was late at night, I left it until the next day. Took a long time but I managed to put all the stitches back on. Now I make sure the protectors are tightly attached to the needle tips.