Lately it's been pedals. I started riding Eggbeaters last year because the Bebops I grew up with are rare as hens teeth these days. Used pairs can be found for cheap all day long on ebay and craigslist and since I own so many bikes, might as well stock up. They're easy to take apart to overhaul and rebuild kits are cheap if they're needed.
Somebody mentioned locks and I got lucky there, basically one and done for me. A birthday gift from my dad when I started college was the Kryptonite New York chain paired with a good shrouded Master Lock he had in the shop. It's no featherweight at 15 pounds but I have been able to confidently lock my bike anywhere in the San Francisco Bay Area for 15 years without worrying about it. There's been more than one instance of bikes on the same rack as mine having their locks cut and stolen but mine was left alone. It's also long enough to go through both wheels. Won't trust or use any other lock.