I prefer individual hex keys to a multi tool because they are easier to get in to tight spots. You can also leave the sizes that you don't need at home.

Steel tyre levers are narrower than the plastic ones and are easier to get under a tight bead than the wider plastic ones.

Finally a small spanner for those mud guard stay bolts 

I ALWAYS carry a spoke wrench. And of course a tire pump and patch kit which aren't necessarily in the "tool" category.

It's interesting, the different opinions of necessary. I don't even own a spoke wrench, much less carry one on a daily basis, and only vaguely have an idea of how to use one. 

Early in my cycling career I did have wheels that suffered broken spokes. I moved to 36 spoke wheels, and have been care free ever since. I did carry appropriate length replacement spokes for awhile. But it's been so long now without problems, I haven't asked for spokes the last couple of bikes I bought.

Perhaps I ride under a golden star. I'm no mechanic. I can change a flat and do the simplest of adjustments. My approach is to take my bike to a qualified mechanic before a tour. That method has served me well. 

Thus, I carry the typical flat changing tools, and allen wrenches. Flat head and Phillips screw drivers. Now I have a bike with couplers, I carry a wrench for that. I have had a small adjustable wrench, but think it might have disappeared. I did have a good quality, small pedal wrench that also disappeared. I blame Jacinto for taking my tools and not putting them back. He, of course, is innocent. 

Not exactly tools - but I carry a small pair of scissors. They've come in handy a number of times.

Kelly, I use a spoke wrench to keep the wheel true, and to keep the spokes tight if I find loose spokes. I true/tighten spokes regularly. My last broken spoke was 20 years ago.

I take way more than I need, but for me it's part of the being "totally self-sufficient" gratification that I get from touring... the fact that everything I need is with me. I suspect that's going to be changing in the near future as I get tired of carrying around things that I don't use, but for now....
I'll be interested in reading the responses of the couples who travel several months every year.

Tools:
patch kit
spare tube
emergency tire boot 
tire tools 
Crank Brothers speed lever
25-in-1 tool  
small needle nose pliers
small crescent wrench
pedal wrench 
saddle wrench
grease
oil  
Fiberfix
cleaning cloth
degreaser
degreasing hand cleaner
duct tape 
electrical tape
handiwipes
miscellaneous nuts and bolts  

My tool kit is so close to Mark Bigham's that we may as well say they are the same.   Obviously, great minds think alike and assemble similar tool kits.   Perhaps Mark and I should assemble some spare kits and start selling them as the "Great Minds Tool Kit."  Of course, having the tools is only half of the battle; you need to have the skill and mechanical aptitude to be able to effect roadside repairs with the tools.   And that's where I'm sometimes not so talented...

I carried a pedal wrench a long time ago but have no use for it now because it has been more than 20 years since I owned pedals with flats for a spanner. For decades, my pedals require a 6mm or 8mm hex wrench for installation.

My goodness! That might be more than I would consider carrying although without seeing photographs, I may be overestimating the volume of the stuff you have.

The best tool to have is a well-maintained, inspected and well designed bike to begin with, although that should go without saying. I prefer a compact approach tools. My on-the-bike tool kits are inspired by the following, specifically toolkit B.

http://pardo.net/bike/pic/fail-003/000.html

I do have a couple of old Cool Tools, as depicted on that page. It would replace the small crescent wrench, chain tool and most of the Allen wrenches in one package. If I was going on a long distance/expeditionary tour, I might take that instead of my usual compact tool kit for riding in relatively civilized areas. it is fairly large and heavy, but well thought out.

 Well, we qualify as ‘couples who travel several months every year’ as much as any on this site I suppose.  Our tool kit is pretty minimal, probably closer to Kelly’s than Mark’s.  Decades ago I used to be at least a reasonable mechanic and carried more - including a chain tool and spare links and a spoke wrench and spare spokes.  And I still pride myself on my finest moment as a bike mechanic, when I managed to straighten Rachael’s warped wheel using a spoke wrench and the pavement to shove the warped rim against.  It was totally warped after I caused her to crash in the White Mountains of Vermont when I lost my head and stopped right in front of her to look at a waterfall, looking more like a figure 8 than a circle when I started, but I straightened it enough to be rideable for the next several days until we found a bike shop.

And after showing this to Rachael she reminds me that nearly the identical thing happened four years later on our ride from Nice to Lisbon.  It was nearly the identical situation - about a day and a half from Lisbon I ruined Rachael’s derailleur when I flipped it upside down in the sand to repair a flat tire.  The same solution applied, and she rode a wine-speed the rest of the way to Lisbon.

And actually the chain tool has come in handy more than once when I think back on it.  I really should carry a spoke wrench again, and will think about it.  Here, the signature event was our first tour of Europe 30 years ago when my derailleur broke dropping out of the Central Massif in France.  It was remarkable: after nearly 2,000 miles that had taken us across the Swiss Alps into northern Italy and through mountainous southern France we were just dropping from the final real climb of the tour when it broke.  I removed the derailleur and a few links from the chain and converted the bike to a one speed and rode it that way for the final 300 miles back to Paris.

Now though we don’t carry much at all.  Partly because I’m really no mechanic and can’t solve many problems anyway, partly because we start longer tours with a freshly maintained bike and new tires, partly because I’m philosophically inclined to give bike shops our business, partly because we bike in pretty tame parts of the world, and partly because we’re fortunate enough to have the resources to buy our way out of a real jam somehow.

So what do we take?    I think this is about it:

• Tire repair equipment (levers, patch kit, tubes but no spare tire, 2 pumps)
• Multi tool (Allen wrenches, slotted and Phillips screw drivers, knife blade)
• Crescent wrench 
• Needle nosed pliers
• Various small screwdrivers, such as for repairing glasses frames
• Grease and chain lubricant
• Pedal spanner, for packing and unpacking at the airport
• Miscellaneous screws, bolts, washers, shoe cleats, etc.
• Electrical tape.

Well, I was wrong.  I see I actually do have a spoke wrench in the kit, and I think in a pinch I could remember what to do with it again.  No spare spokes though.

This got me to wondering if anyone here has used a FiberFix spoke? I carry one for emergencies but have not had cause to use it. My kit is quite similar to Scott's, but I also include (maybe he just didn't mention) a variety of zip ties.