I bought a second bike computer for half price in January after buying the first a few days earlier. Didn't really need the second computer but it'll go on a second road bike.
And bought a second 2012 era Wahoo cycling pack for the iPhone 3/4/s. I still have an iPhone 4s and the Wahoo pack's ANT+ adapter and magnet based speed/cadence sensor are a bargain at around $10 now. Those packs originally cost around $150 and while the tech is obsolete now (bulky ANT+ case for the old iPhone) the sensors alone are worth the money. And compatible with my XOSS G+ bike computer.
Recently I bought a good set of downtube friction shifters from another BF member. Didn't really need these either but I got 'em in case my Suntour GPX downtube index shifters go bad. The GPX shifters are great in index mode but are mediocre in friction mode.
Bought a second Peal Izumi aero race fit jersey. Didn't need it either. But the first fit so well, when the other went on sale for 66% off the MSRP I got it too. Not sure if the jersey was any "faster" -- I've worn it only once on a really windy day -- but I could feel much less buffeting around in crosswinds. That alone was worthwhile. Felt much more secure than my looser fit jersey in crosswinds.
Got three identical older model KMC chains, just after KMC changed their catalog and either renamed or eliminated the Z72. The "old" Z72 was heavily discounted on Amazon, including the Missing Links. Chains usually last me a couple of years so that's one less thing to worry about for one bike.