I don't actually like HUDs. I mean, if they're pretty, then so be it, but most aren't and despite how every developer seems to be striving for uber cinematic quality, the infamous HUD still remains, and is possible getting worse in some cases... looking at you Conviction. To elaborate on that point, Conviction has one of the most intrusive HUDs if seen for this specific genre. I.E.a detection ring that actually says detected and permanent crosshairs... wtf to that.
Moreover, if you look at Gears of War, it has what EPIC calls a "Fading HUD" which means if you're not using it, it disappears. This concept was arguably founded by Metal Gear Solid. In the early days of Solid and SOL your health bar was not visible unless something happened to it, I.E. you got shot, and your item/weapon icons were only present if you had something equiped. On the topic of SOL, I've been playing MGS2 HD quite a bit lately and yes, it's lack of HUD is one of the things that made me want to bring this up. I love it!
Dead Space is probably the only game this generation that has really striven to eliminate said intrusive HUD. Though, I think it's inevitable, someone is gonna say that HUDs are here "because teh n00bs needs them"... and well, they'd probably be right. Still, that's not an excuse IMO, because there can always be a HUD toggle. Just like the helper icons in Gears of War. A great example of how a HUD can be removed is the R6 Raven Shield "realism mod"
It basically removes every helper in the game, including crosshairs. The only way to aim 100% is to use the iron sights... fair enough. Still all is held together by your tactical goggles. The way those modders implemented them "onto" the screen, like SW Republic Commando, was genius. I love that too.
In this genre though (action/stealth) I think a degree of on-screen information is kinda mandatory. Though, notably there have been several substitutes for stealth meters. Sadly the B&W filter is actually one of them... meh. Riddick did it better. There's always the old "the suit lights up" method, but that really only works if you're avatars suit has lights on it. I have a method to solve this particular one, but I'm not sharing it... umm, because it's mine, mwhahaha.
Moving on, weapons and such can be solved with the light crisis. Depending on the weapon that is ready to be equiped, a little light will pop up on it's holster. As for ammo, well I guess that could be handled with lights too: brighter/numerous lights for more, apt for apt. Plus detailed visuals that let you "see" what your avatar is carrying. And, as I said, the option to turn on the traditional HUD should always be present... just not mandatory.