Sometimes an invention comes along that is so simple, awesome, and bound to change the world of canned drinking so drastically that you just have to stop and ponder, "Why didn't I think of that?" Well this isn't one of those, but it is can related. Introducing the Resealable Can by Ukranian inventor Johan De Broyer!
You pop the top as usual with this design, and then when you want to re-seal it, you turn the pop top tab and it completely closes up the can again, good as new. The inventor says his invention can create a completely gas-tight and liquid-tight seal. An added incentive toward this idea's adoption is a space on the resealed top for advertising.
Now I know what you're thinking, "I'm a big boy, I can drink a whole can of beer/soda, so why would I ever need to reseal one?" Two words: Because you just peed in it.