A comprehensive list is just impossible, but some oddball tools that you'll probably need are:
30mm socket for the nuts that hold the radius and trailing arms to the frame ears (also fits the nuts holding on the transfer case output flanges);
15/16" socket and wrench for the for the fasteners that hold the radius and trailing arms to the axle;
2 1/16" hub nut socket;
12mm 12-point socket for the exhaust manifold bolts;
13mm 12-point socket for the brake caliper bolts;
9/16" socket and wrench for the driveshaft bolts;
17mm wrench and 17mm deep and shallow sockets (there are M10 bolts everywhere on the Disco and your Hella 4k's are M10 as well)
19mm wrench and sockets for your OME shocks;
13mm wrench and sockets for your rubberized shock tower securing rings (and 13mm is another very common size)
11/16" flare nut for your female-ended Paragon hoses;
14mm flare nut for your male-ended Paragon hoses;
9/16" 12-point socket for the bolts that hold the brake rotor onto the hub;
17/16" impact socket for your wheel lug nuts;
Pozidriv 1,2,3 and 4 (I think the set screw on your parking brake is a Pozidriv 4);
9/8" wrench for your crankcase drain plug (this also works on your Power Tank's regulator flare fitting);
22mm wrench and socket for your panhard rod bolts;
a very long 14mm wrench for the 12-point bolts that hold the swivel ball housings to the front axle (a socket won't fit here);
11mm socket for the swivel ball level and drain plugs;
1/2" square socket for your swivel ball fill plug:
You should get an entire set of extensions. The Snap-on Wobble Drive Plus in 3/8" size are my favorite:
I also think it's wise to have adapters for all of your drive sizes, e.g. 1/2" to 3/8", 3/8" to 1/2", 3/8" to 1/4", 1/4" to 3/8", etc.:
And also universals for all of your drive sizes:
For my own use, I prefer the Knipex plier wrench over the standard adjustable wrench:
The plier wrench's jaws tighten as you crank down on the handles and you get less of a tip spread problem than with an adjustable, so you get more cranking power with the plier wrench than with a similarly sized adjustable. The plier wrench also has a greater range:
The plier wrench is really well designed and lets you use the pliers almost like a ratcheting open-ended wrench. The handles let you open the jaws just enough to reset the plier 60 degrees without having to remove the plier from the fastener. It's hard to explain but if you see it in use you'll immediately see the advantage. You'll probably need an adjustable too though. It's pretty much inevitable. But I definitely prefer the plier wrench for most jobs.
I also find a magnetic pick-up tool to be very handy:
The larger ones are strong enough to fish out broken halfshafts and other vehicle carnage:
I have both the biggie one and the micro-sized one that resembles the radios used by the Unicorn police in
Johnny Sako And His Flying Robot. The little telescoping magnet is really useful for picking up dropped screws and such.
Those are ones off the top of my head. There are, of course, many many others. I think Thom's advice about using your field set to service your truck is really good advice. Use your field set whenever you work on your truck and add to that set whenever you need an additional tool. This is much better than using your toolbox while at home and trying to remember what you need to take for a trip. I now do this for both my Defender and my motorcycle.
