I won't address weight here because the other posters have already covered it. I will talk about my personal preferences. First, here's a little information about me and the climbing I do. I started climbing when I was 10. I've been leading trad since I was 13 and I've been really into aid for about 5 years now. I've used a good portion of the pro on the market. I've spent a fair amount of time in Yosemite, the Rockies, Utah, Joshua Tree, Squamish, and a number of other places around North America. My main playground is North Carolina and it's long granite cracks and faces. I've climbing both weathered and desert sandstone, limestone, and granite.
That said: BY FAR my favorite piece of passive pro has been the Metolius Curve Nuts. I prefer the old ones over the current ones with the fixed cable. If you can find those they weigh a bit more but give you a few more options. Being aid inclined these days, options are the ticket for me. The Curve Nuts place and clean VERY well. They are easy to assess. Most importantly they are bombproof. I like straight taper nuts a lot due to the extra security of the placements. The Frost Nuts are nice but they are somewhat limited in their usefulness by their straight sides. The Curve Nuts are simply awesome everywhere I bring them.
It's important to note that no one nut set will get you thru every situation. I generally carry a mix of Curve Nuts, BD Stoppers, and Offsets on long routes. These three complement each other EXTREMELY well. The Offsets are critical gear for me on Yosemite granite or anywhere with a lot of pin scarred or flaring placements. The Curve Nuts, however, often work in some of the same placements. SO if I carry just two sets it's usually the Curve Nuts and Stoppers. You can't go wrong with these three sets on any rock anywhere.
As far as cams go NOTHING replaces the Camalot. It's simply the most versatile cam out there. This is one case where trying too hard to save weight can hurt your efficiency. I've found that efficiency of systems in climbing is the most important thing on long routes. Dropping weight is one way to improve efficiency but there's a point where dropping more weight can hurt efficiency. There's nothing like being WAY out on lead with your only placement for the last 40 feet and discovering that the extra cable on your lightweight DMMs or Metolius FCUs makes an otherwise bomber placement kinda sketchy. The double cables can be kind of nice in horizontal placements but it's not like Camalots are sketchy here. The extra range is also extremely comforting on those grab and go placements where you jam one in from a sketchy stance. I've also found the camalots to walk less and work better in flares then any comparable cam. For all these reasons Camalots will always be my cam of choice.
Two other cams I have to mention are the Metolius TCU and CCH Aliens. Both of these are pieces of gear that I LOVE. The Alien always has a way of being the most secure, comforting placement in some of the worst situations possible. It really comes down to the width of the head and lobes as well as the angle of the cams. The angle does sacrifice a little of range but that's how cam angles work. More camming force-------------More range. That's part of why the double axle of the Camalot is such a big deal. It manages to get both of those characteristics. Anyway, Aliens rock. The TCUs complement the Aliens extremely well. The are two places the TCU really excels. They are terrific in shallow vertical cracks and they work really well in horizontals. However, if I were to choose between the Alien and TCU for a micro cam it would be Alien every time.
The new C3 and Mastercam are both nice. The problem with the C3 is it's just too finicky. They get gunked up too easy. They are a nice concept but I feel the execution is just a little off. The Mastercam is great. Some people might prefer it over the Alien for good reason. I've just used the Alien so long that it's become my sidekick. The Mastercam is very comparable to the Alien though.