I don't see a particular advantage to those things. Quirrel doesn't fear a single nuclear weapon -- Voldemort can survive such a thing -- he fears nuclear annihilation or MAD, which is a separate matter and not much overlapped with an individual bomb. Muggle weapons are useful and a matter that might require someone to go outside of the country to get... but even a firearm requires training that Harry doesn't have, and can not kill a Dementor or a Troll. Where firearms could threaten the average unaware Wizard, we've seen that most major players are aware of firearms (including McGonagall, Dumbledore, and Snape, see chapter 61), and thus it would not likely fall under things that a Muggle Expert's sons would not recognize.

And the set of things that Rationalist!Harry knows can resurrect someone is very, very small, and not much overlapped with the Muggle world. Most rituals and potions require ingredients that already have significant magical power.

The "things that Fred and George can't recognize" is an interesting set. Canon!ArthurWeasley isn't very knowledgeable, but he at least had an interesting in electrical power, heavy-than-air non-magical flight, and chemical fueled engines. I think we can expect him to be of similar intelligence or smarter in MoR. It's possible that he's better at hiding his interest in Muggle technology or that Rationalist!Harry intentionally wrote non-standard descriptions for the items, but that seems unlikely. ((We're also taking 1990-ish tech, so some 'obvious' stuff from today either didn't exist or would exceed his budget.))

The first thought is dry ice, and the tools necessary to maintain it. Rationalist!Harry has broken several rules of transfiguration, including "don't burn anything", but the ability to transfigure CO2 is probably the easiest way to 'safely' violate that rule, not terribly expensive, but not within his normal abilities to easily produce otherwise.