Had a weird crash happen with NEI and Techguns, along with some other mods I installed. The screen blacked out (my entire screen, not just Minecraft) for a split second, and then the game closed. Happened both when creating new worlds, and loading worlds. The conversation I had with the TechGuns dev (albeit a very short one) is linked, which also contains the crash report. Also linked is the conversation I had with mezz of JEI fame.

pWn3d1337/Techguns2#152
mezz/JustEnoughItems#1675

Apparently NEI fails to access JEI stuff and as a result crashes. Will test with just NEI and JEI, and if it still happens, then integration between the two mods should be fixed.