I always keep boxes of doms in my luggage and at least one in my wallet. Once my gf was looking through my stuffs and she's holding them with the look, 'What's this?' I've always got this backup story: In times of emergency, condoms can be used to fill up water! It can save your life!
Sidetrack: Once in a chinese neighbourhood, a nine year old kid (his dad doesn't care him) who we knew, he was playing in the garden with a blown up condom. It was roughly the size of his torso!
I got up to him and asked where he got it, he said he found it in his dad's stuffs. Can't really stop him or tell him what's that for. But, he's swinging it around so jolly happy, and the older folks sitting on benches were just staring at him blankly!