For the lower, a couple of roll pin holders and roll pin punches really help, although they are not necessary. Likewise with the stock wrench. You can do without it, but they are cheap and they make the process a lot easier to do well, without grief and aggravation.
If you are going to assemble your own upper, you really need the upper receiver vise block and armorer's wrench. A roll pin holder and punch for the gas tube pin help. You can usually rent or borrow a torque wrench with the correct size drive from your local auto parts store (or garage, or mechanic buddy). If you have a couple of large c-clamps you can do without a vise, but it is a lot more clumsy.
As Doc pointed out, some handguards go together much better with a dedicated tool. Yankee Hill is a good example. Others don't require anything special. When you're deciding on your handguard, check out the installation instructions on the manufacturers' web sites. That will tell you if you need any specific tools or thread lockers to get the job done right.