So so far we know of a few different builds. Someone please correct me if any are wrong or missing.

Google:
*yakju (vanilla)

Samsung:
*yakjuxw (?)
*yakjuux (Canada)
*yakjusc (DoCoMo?)
*yakjukr (SK Telecom, S. Korea)

Anyone know what the Verizon LTE region is? I assume it's also a Samsung one...
Current Device:
LG Nexus 4 (GSM, 16GB)
ROM: Stock Android 4.3
Baseband: M9615A-CEFWMAZM-2.0.1700.84
Build: JWR66V
Kernel: 3.4.0-perf-gf43c3d9

Previous Devices:
HTC Nexus One (AT&T Version)
ROM: Cyanogenmod 7.1 (Android 2.3.7)
Baseband: 32.50.00.32U_5.12.00.08
Build: GWK74
Kernel: 2.6.37.6-cyanogenmod-01509-g8913be8shade@toxygene #1

Samsung Galaxy Nexus (GSM Version)
ROM: Stock Android 4.3
Baseband: I9250XXLJ1
Build: JWR66V (Samsung takju)
Kernel: 3.0.72-gfb3c9ac