I'm not proud of this one, but it did get me home when I was running out of options.
Due to a somewhat convoluted set of circumstances, I found myself in the middle on nowhere with a flat tyre, both spare tubes already used, and no usable puncture repair kit. I did, however, have a Park Tools self adhesive tyre boot. As a very last resort, I tried wrapping this firmly around the inner tube, slipping it back into the tyre, and pumping gently. To my astonishment, I couldn't hear a hiss, so kept pumping until the bike was rideable. Even more amazingly, I then rode it like this for about 50km back to event HQ, with no further drama except a slight judder from the rear wheel at high speeds.
I note that this morning the tyre is flat, so this is very definitely just a get-you-home solution. But it does seem to work as a last resort!
Me, I'll be super-careful to make sure I don't pick up an old puncture kit with a dried-out tube of adhesive in future. But I'll be sticking with my policy of carrying a Park boot on longer rides, too...