Specifically, Extra Utilities, Uncrafting Table (by jglrxavpok), and Gravity Gun.
Why this combination specifically? Well, because:
- Craft a ton of regular GravityGuns, you can do the Division Sigil ritual to self-induce lightning, then get a ton of free supercharged guns. Now just go to the uncrafting table and uncraft all of them, there you go, free nether stars (ok, not free, but they might as well be, they only cost 5 XP levels to uncraft). If you want more than just nether stars, craft up a Nether star gen and throw them all into the generator, there you go, insane amounts of power (which, if you do the math, will produce 40K rf/t, and 48M in a minute).
- By uncrafting an item made from unstable ingots (e.g building wand, block of unstable ingots) in the uncrafting table, you can glitch out the ingots and bypass the explosion timer. (And if you're using tinkers, you can use a crafting station instead)
If you're looking for something less specific, I would say dimension-building mods (take Mystcraft or RFTools, although personally I recommend Mystcraft since you don't need to worry about power or any advanced machinery and literally just use a pen and paper, although RFTools comes without instability plus you can absorb certain objects to obtain dimlets, so i guess each has their own perks. Using them together, however, completely breaks RFTools since you don't need to have the dimension tab in the dimension builder [and therefore, waste power] and can instead use a book).
Draconic Evolution is another one. Yes, it is a mod designed for late game players (very late game in fact), but that doesn't mean the stuff you can make with it is not insane.
Tinkers is definitely up there (on a scale on 1 to 10 though, maybe a 6?), of course, it it isn't all Draconic Evolution-y where you have hilariously overpowered tools. But it's pretty great that you can make a tool that you like and one that works the best. When it works, it works good. (And let's not forget those XP berries, those are hilarious and pretty much outdo any mob XP grinder, if you're patient, that is)
Extra Utilities is also great for other reasons (building wand i love you). And a couple other things (cough, transfer pipes work with almost any item that has an inventory, cough, unlike itemducts from TE which only work with vanilla and TE blocks, cough)
Speaking of, TE is a great mod. Pulverizer, barely on the 5th ingame day? Ore doubling on the 5th ingame day is great, that way I don't need to worry about running out of iron (or anything else, but let's be real here, iron is used to death in most tech mods). (still, it has it's issues, cough itemducts cough)
Well i've rambled for long enough. and wow this is a long post