Something everyone will use

I would give them the URL to the Cool Tools Web site.

I think a small tool kit that comes in a self contained case is a good gift for many, just something that can be stashed in an apt, car, dorm, etc. They are available a various hardware, home improvement outlets. I've found that just have a set around has allow my friends and relatives to get simple jobs done without the threat of having to track down tools from the garage. The one in my kitchen gets more use than a lot of my better tools in the basement/garage. (hanging pictures, puttng together simple furniture, fixing loose railing, etc etc.) something like these: Craftsman Amazon cheapie

When you've got a hammer, the whole world looks like a nail. In some sense, it sounds like you're asking the CT community to identify the mother of all hammers.

I think you'd be far better off getting up to speed on the last 100-or-so CT reviews and seeing if any would nail a problem in your friend's environment. Quiz friends of your friends to see what they think about your ideas. Make sure that your friend actually wants the problem solved -- sometimes we like our problems.

Ultimately, giving gifts involves some risk-taking. That's part of what makes it fun. Putting in the due diligence to identify cool tools that is a likely fit for your friends' needs is definitely a worthwhile task.

If your friends are appreciative of your effort, you could suggest that they "tool it forward" in a similar fashion.

People have a universal need to repair things. Common mishaps include tearing clothing and getting ink on it. So good candidates would be Tear-Aid (in the Cool Tools catalog, page 72) and an ink remover like Amodex (on Amazon).

One of the good tweezers on p. 438 of the CT catalog would also eventually be appreciated by everyone. I just gifted myself the version with the magnifying glass.