A good allen wrench can save a lot of time and effort because it will never strip, and you can even use ball allens that won’t strip. This is especially useful when tightening a motor in a tight place, where you would normally not be able to put a motor or where you would have to do multiple revolutions of those L-allens. You can also get things tighter with an allen that doesn’t slip. Some good companies are hudy and rd logics, hudy is the higher end brand, but is a bit more expensive. The shafts are also more rigid, they don’t bend or twist, and have rounded shafts to better rotate in a hole. These can be found on ebay.
Calipers (accurate ones, not toy plastic ones) are also useful if you want to check alignment or want to know an odd distance or the size of a crushed spacer.
A low capacity, high accuracy scale (100-1000g) is useful for comparing weights of small mechanisms with slight differences (for example, using bar instead of standoffs), and can also be used to measure weights of parts that aren’t given, for example, standoffs, standoff couplers, washers, spacers, collets, and screws.
And then of course is the high capacity scale for weighing robots and arms.
Another scale that you might find useful is a hanging scale (the type with a hook at the bottom). This can be used to gauge the force necessary to move certain parts of a mechanism (an arm, elevator, a winch, or something else), and can be useful when counter-tensioning (also to make sure that your rubber bands haven’t lost too much of their spring).
What do you need high precision scales for? Actually just scales in general, I don’t really think weighing parts is that useful. I guess it might be nice to know how much your whole robot weighs, but a bathroom scale is probably good enough for that. If you cad your bot, you can use the weight of each part to find more useful things, like center of gravity.
Aside from allen wrenches, I think the most important tools you can have are regular wrenches and a dremel.
I find for vex you dont normally even need a scale, seeing as there is no weight limit. The more important things is the relative weight of different parts, so you can judge what is better for certain applications.
Just bear in mind that if you’re using these for competition use, they must be identical to the ones that Vex sells. Round shafts would not be identical.
He was making reference to an allen wrench that had a round shaft. I know it sounds a bit like he was making reference to an axle.
A ball head 5/64 is amazing for getting those motor screws in hard to reach places! And should be a must have!
Also a metric set is handy or at least 2.5mm and 1.5mm to tighten pneumatic fittings! Can’t have any leaking! ( just don’t over tighten them)
Also one of these is really handy to have or similar to this just look for one that cuts 4mm tubing! This makes sure all the tubing is cut straight again reducing chance of leaking! http://www.automationdirect.com/adc/Shopping/Catalog/Pneumatic_Components/Pneumatic_Accessories/Flexible_Pneumatic_Tubing_-a-_Hoses_Accessories/TC-12
These are pricey but nice if you like clean wiring and don’t want sharp edges on your zip ties 
[http://www.amazon.com/gp/aw/d/B0002I1Z8Q
A non competition legal pressure gauge that works with 4mm tubing is also really handy to use to calibrate your pressure regulator along with check for leaks! Obviously you remove this after you finish calibrating because its not legal.
A pair of tweezers is handy sometimes.
Also wire strippers that also can cut screws without ruining the threads for when you need those custom length screws! I used this a lot I only purchased 2" screws and cut them to what I needed.](http://www.amazon.com/gp/aw/d/B0002I1Z8Q)
I find these invaluable for tightening flat -head and phillips-head screws in hard to reach places:
http://www.harborfreight.com/6-piece-precision-screwdriver-set-6904.html
They are long, and small enough to fit through axle and bearing holes.
A quality sprue cutter is nice for removing tight zip ties without damaging wires/tubes. I have this one:
http://www.amazon.com/gp/aw/d/B000BL8K6Y
I have one of these and it works well:
http://www.harborfreight.com/cable-tie-tool-66521.html
Harbor Freight also sells a higher quality tightener like the one Android4life posted that has decent reviews:
http://www.harborfreight.com/adjustable-cable-tie-gun-67076.html
I keep some bolt cutters to cut axles when they are hard to get to in the robot.
We tend to ue lineman pliers for this. They are very helpful for cutting axles and metal strips, as well as for tightening vinyl nuts when we have them sitting next to us. They are also heavy enough (in most cases) to be used as a hammer if needed.
i recently bought a dremmel for cutting axle bars and metal, works really well but can b dangerous …
Yes, Always wear safety goggles! I would also recommend getting one of these: | Dremel
assuming you don’t already have one. They are better then the normal cutting wheels from my experience because the hole in the normal cutting wheels would “egg out” if you put too much pressure on it. The EZ lock wheels have a reinforced attachment hole, and as the name suggests, they are more easy to attach.
+1 we also use the EZ lock dremel attachment.
Last year we also invested in a metal shear. It’s super quick to cut plate and other things, which makes it more desirable in some cases than the dremel.
hi, yes i already bought an easy lock system works nicely, i am considering getting this … if anybody has one and can tell what they are like i would b greatful …
Which tool gives the cleanest cut? metal shears, dremel, hacksaw, tin snips, or something else?
We have one of those and it is very nice 
I would buy one if it were me.
The fastest cut for us usually comes with tin snips, pliers to bend back the metal, and a file to clean it up as tin snips leave sharp edges.
A Dremel will provide a cleaner cut and in tighter places but it takes a lot longer.
I have one of those as well, and highly recommend it.
I also have a Dremel drill press (https://bigtoolstore.com/0-55289/Dremel-Access/D--DREMEL-DRILL-PRESS.aspx ) mounted over a sliding X-Y table that works like a hand-crank milling machine. I use it for cutting slots and squares out of different materials, especially polycarbonate.