My tools that I use every day for work are mostly Snap On. But I just bought a 39.99 21 piece 3/4 drive socket set at one of those traveling tool sales. 1" to 2" sockets. They are by no means Snap On quality, but they will do the job. As to the orriginal poster, I would highly recomend an air grease gun but it is not a neccesity. I think some things that your typical tool box might not have would be:
1. liquid/air pressure gauge
2. tire valve core tool
3. adapter for putting liquid in tires
4. LARGE strap wrench
5. Cheap ball pean hammer
6. Cresent wrenches, (I hate them but tractors love them)
7.cotter pins,hair pins, clevis pins,ect
8.OFF,sunblock,bandaides
9. 2 towels (the dirty dirty one and the "clean" dirty one)
10. Saftey glasses, earplugs, and gloves
and the most important tool is that little voice that you can just hear over the roar of that big powerfull tractor... When it asks you "are you sure you want to do that?" pause for just a second and be sure you are safe.
HAPPY TRACTORING