[hi-v-rocknroll]

Back in the day, even on a low-end steel Miyata mountain bike, I had to have QR wheel and QR seat post keyed locks because of theft. They consisted of an epoxy-coated offset plate with a hole at each end and a miniature luggage lock. In general IMO, it's not worth having an expensive bike because it's just going to get ripped-off and likely lacks significant benefit over a middle-market one. (A friend of mine had a $8k USD road bike stolen in downtown Mountain View right in front of every passerby in the busiest area where cops pass every 10 minutes.) Also, the only time I ever forgot to lock my (undersized jacked up with very long seat post and handlebar extensions) Miyata in the rack at home (apartments) in Davis CA was the very time it was stolen.

For dry climates: wax lube. Wet lube is only for rainy climates and attracts dust like mad. Chain guard is a must for non-leisure riding.

And if you don't like changing tires very often and don't mind the extra free exercise of added rolling resistance, kevlar armor bands are a must have with green snot slime. Still have to carry a vulcanizing patch kit, levers, and a pump because goatheads are pure evil.