Name: Schematica
Link:
Click here
Version: 1.6.4
Reason: This is a really handy practical mod. Many mods in FTB feature tricky block structures, such as IC2 factories, automated farms and Buildcraft quarries. When starting a new world, remembering what goes where can detract from the fun. With Schematica you can export block layouts as .schematic files, then use the mod to import them into the world as a ghost image to guide you. This mod lets you copy whatever you want, from a Thaumcraft base, to a village, to large sections of your world.
Name: Witchery
Link:
Click here
Version: 1.6.4
Reason: I find this mod interesting because it initially takes a quieter, more Minecraft-like approach to magic, in contrast with the flashes and bangs of Thaumcraft and Ars Magica. It becomes quite complex, though, and soon you'll be bargaining with demons!
Most of the mods I had in mind have been posted here already, but in general just shoving all the mods in this topic into the next pack would make it absolutely stunning. Riddled with conflicts, possibly, but stunning.