Being an old school RPG, a significant portion of Gamma World's ancient artifacts are weapons or weapon systems. There are six different types of pistols, the most interesting being the slug throwers (which fire rubber bullets for riot control and stun targets for 1d6 minutes when they deal cumulative damage equal to one-half their total) and black ray pistols (which instantly kill any unshielded living -- but not robotic -- target with a successful hit). There are only four rifles, perhaps the deadliest being the fusion rifle, which blasts its target with two beams of intensity 18 radiation, though it's not stated whether the firer needs to roll to hit twice or just once.
There are energy-based melee weapons, too, whose unique characteristic is that they deal flat damage (10, 20, 30, etc.) rather than a range (1d10, 2d10, etc.). Of the six grenade types described, two deal instant death and/or disintegration to enemies caught within their blast radius, continuing the trend of extremely deadly weapons in Gamma World. This trend reaches its zenith in the sixteen bombs and missiles also detailed, from small backpacks full of explosives dealing 6d6 damage to all in their blast radius to missiles carrying neutron bombs that deal instant death to living things.
There are ten types of powered armor, divided into "defensive" and "offensive" types. Curiously, defensive armors generally lack force fields, making them a lot less useful as protection than the offensive types. Offensive armor also tends to have many more extra features, like anti-grav flight, built-in medikits and communicators, and so forth. From my perspective, though, it's the force fields that are most interesting part of these armors, since the provided round-by-round damage reduction in addition to a lower armor class. This is, I think, the first time we see anything of this sort in a D&D-derived game.
There are seven vehicle types, most of which use anti-grav technology. There are two types that don't (and a third that sometimes doesn't), but both are explicitly explained as being archaic by the time that civilization was destroyed. I consider this important information, since it emphasizes the fact that Gamma World's fall happens in the future, not the 20th century. Thus, we should see very few, if any, examples of 20th century tech kicking around in the 25th century, but this is a topic to which I'll return later.
A lot of attention is given both to energy cells and to I.D. devices, both of which come in many varieties. Having access to a goodly supply of these -- and the right ones -- was, in my experience, one of the keys to success in Gamma World. Nearly every technological device requires an energy cell to operate and these cells are generally quite inefficient, being used up after somewhere between 6 and 10 uses of a device, with a few exceptions. This was almost certainly intended to keep a rein on the use of high technology in Gamma World and rightly so, given its effectiveness. I.D. cards, meanwhile, serve a similar function, limiting the ability of the PCs to get into Ancient installations where they might find functioning high technology.
Another limit readily apparent on Gamma World's technology is that it was clearly designed for use by pure strain humans. The text often notes that humanoids with visible mutations might be unable to make use of many devices. This is particularly true of anything computer-related, since it seems that these machines only respond to pure strain humans or humanoids who can pass for such (mutant animals are utterly incapable of passing muster).
Looking over Gamma World's rules for high technology, what's most evident to me, aside from its lethality, is how often the rules are either vague or employ some sort of new approach that one did not see in D&D. I've already noted the ablative effect of force fields, but there's also the stunning rules and cases where high technology temporarily boosts ability scores or hit points. In other cases, what we see are no rules at all, just a suggestion that "device x does y" but without any quantification of how it does y or how often or with what effectiveness, leaving such things to the referee.
As a kid, I don't think I ever took notice of these facts; my friends and I just rolled with it and came up with answers as needed. Nowadays, I can't help but notice both the vagueness and the ad hoc sub-systems created to patch over holes where D&D provided no rules or no model on which to make rules. I don't think this is a bad thing by any means. Indeed, I think I prefer this approach all things considered. However, it's definitely one that is alien to so much of contemporary game design and the culture of play that's grown up around it. For that reason alone, I suspect Gamma World would be a hard sell for gamers who expect rules to be both exhaustive and meticulously consistent -- their loss.