Hoarding nickels, although it sounds nuts, is actually a good thing to do. It's a no-lose proposition.
The copper in a nickel is worth about 8 cents, and they haven't started making zinc nickels yet, so you don't have to sit there squinting at them like you do pennies to sort out the zinc ones. I think they're supposed to start making zinc nickels in a year or two, so get started now.
If nothing happens, i.e. the dollar doesn't crash, you still have money, because nickels are money. If the dollar is replaced by a totally different currency, you have copper you can sell for the melt value at a profit to you of (now) 60%. If the dollar goes into hyperinflation and is re-cast, i.e. if they come out with New Dollars or something like that, that are worth 100 old dollars, either they will keep all the nickels in circulation and say they are now worth 5 cents in the new dollars, in which case you lost nothing; or they will replace all the coins, in which case you still have copper for melt value just like if they replaced the dollar with something completely different.
The only way you would lose would be if inflation went slowly and you just held onto those nickels for years and years until they were worth 5 percent of a very devalued dollar. But at some point due to the cost of copper they will HAVE to start making zinc nickels, and you still have the melt value of your old nickels, so that's really not losing.
Another disadvantage to hoarding copper is it's heavy compared to silver or gold - but it's also less likely to get confiscated if they get too happy in Washington.