Null Rod is so basic. It stops moxen and lotuses. It's playable in pretty much any deck. It's quintessential sideboard.
I grabbed a bunch a year or so ago at market prices, anticipating an eventual bloom. It happened a few months back, then fell, but I think we've found the bottom of the fall, as you can seen from the graph (green in minimum, blue is median) and we're headed into a second price spike. Get in on these under $10, don't be surprised if they hit $20-$25 on the next crest.
And as a long-term hold, these are tough to beat, for one simple reason: Null Rod is on the Reserved List, never to be printed again (says Wizards).