This is an even more nitpicky topic for me than knives are. There's a particular tool combination that I really won't budge on, and the tools themselves have to be designed smart which means screwdrivers need to have usable reach for recessed screws and not be made too thick and wide to reach them (for example I don't want a flathead screwdriver at the end of a can opener bit or something). I also get really annoyed with "21 tools!" when most of the those tools are piggybacking off other tools and the wire cutters count as 3 tools because they have a little stripper notch cut it them. It's a slimy sales tactic that they're all guilty of.
I like one handed opening and outside accessible tools, but I'll compromise on this to get everything else the way I want it. I'm never using a MT so urgently that I need fast one handed opening, it's not the same as knife use for me. It's convenient but not a critical detail.
I do however really prefer "clumping tools" which is a debatable topic. This is when all the tools clump and come out at the same time when you pull one tool. I prefer this because it's easier than getting my sausage fingers in there to get some of the smaller tools out. I like to pull them all out and fan out the tool I need.
Tool list:
-Pliers obviously
-Prefer replaceable wire cutters, this is why I stopped carrying Victorinox
-Philips and flat screwdrivers, good reach
-Can/bottle openers
-Scissors, and not just as an afterthought
-File, with steel and diamond texture
-Wood saw, not used often but I still want it
-Would like one of the tools to be pry bar worthy but I can use the pliers if necessary
-Knife blade, doesn't have to be anything fancy just a good beater blade, I actually don't mind combo edges here
Seems easy enough doesn't it? Why so many tools have to include 3 flathead screwdrivers is beyond me. I rarely have a need for the tiny/narrow ones.
I should probably mention my somewhat hatred for bit drivers (I'm looking at you Leatherman). For the longest time I couldn't stand them because they can't reach anything. At work I sometimes deal with computer components on machines and I'm always working with recessed or "far away" screws and the stubby bit driver is just useless here. I also hate Leatherman's flat bits, they don't bite screws well enough. The concept of having all the bit types is enticing, I just don't like the execution. But, I recently figured out how to modify impact driver bits to fit these bit holders and I've gotten around this with a usable compromise (see pics).
So this brings me to what I've carried for the last couple years. For a while it was this heavily modified Supertool 300:
The reason I went with a Supertool to modify is because it offered the most length of tools and there were 3 models that each had the kind of tools I wanted to combine into one. You can see the custom Philips driver in the bit holder. It also has a t-shank blade holder, which I feel kinda eh about. It's nice because I can have several blade types in one tool slot, but it means I need to carry those blades with me somehow and I don't want a huge Batman belt sheath full of crap hanging off my hip. I have 2 blades in my wallet and that has worked pretty well. One disadvantage is that the blades are shorter to accommodate the t-shank itself, so when dealing something like a hacksaw blade it can only be so effective. One significant advantage of having your file on a t-shank holder is you can pull it out and use the diamond file side to sharpen the multitool knife blade. This is an enormous advantage if you actually need to do so.
This combo also has a nail puller tool which I left in there out of curiosity and I like it a lot, it's extremely beefy. The problem though is that it has to be in the very middle of the tool for packaging reasons, which makes it awkward to use as a prying tool.
You can also see I added Victorinox scissors because they're among the best you can get. They don't lock in place but that hasn't been an issue at all.
Recently I got a really good deal on a Leatherman Arc. I have hated on this tool hardcore because it's kind of BS how they're pricing it. I get that it's "USA MADE" and that's rare these days and I get the MagnaCut blade, but it's like they're pushing for tool+knife money and for me that's a little steep. If I didn't get the deal I got, I wouldn't own one.
But here we are. First thing I did was fit my modded Philips driver into it. It doesn't close all the way but it's working so far. I'm torn on the Free Technology thing too, I like how the tools themselves can all be opened one handed, but I don't care for the butterfly knife effect of the pivots being free swinging. I sometimes like to lock my tool half open for extra reach and it doesn't work as well with this. I'm also not crazy about having magnets in a tool where metal shavings might find themselves. The second mod was getting rid of the horrible wire cutter blades they put in these, that have been known to break apart the first time I try to cut anything more than electrical wire. I put the blades from a Supertool 300EOD in them which have one flat continuous edge and cut much better.
As for the MagnaCut blade, Leatherman apparently harden these on the softer side of ideal, but it's fine for what it is. It's nice if you're not the kind of person that carries a pocket knife, but it feels a little redundant. I'm also not sure why they chose to coat them black when this steel is so corrosion resistant. I also friggin hate thumb studs and wish they'd just cut a slot hole in it like all the other blade tools.
If you're wondering how the Philips driver is made:
I like this a lot. It's a full size/thickness head and bites into screws so much better than anything I've used in a MT, and it's replaceable if I manage to wear it out but it's also made of far better/harder steel since it's for a drill, so I may never need to. This really changed my opinion of bit drivers and there's a whole aisle of bits like this that can be modified to work the same way.
Knife nut & Spydie aficionado 
