I might be kind of strange in this regard but: I hate getting physical presents!
At the moment there are only a few very specific things which I really want or need so buying me something random will just result in wasted money on the presenters side and wasted storage space in my side. Right now I have about 15 unread books next to my bed, I have all the tools (software, mechanical/electrical tools) I will ever need, I have about 5 bicycles which I don't use and the only hobby I have right now is fitness and writing my PhD thesis.
If you want to present me something then either present me an Amazon coupon for the unlikely case that I want to order something specific in the net half year or invite me to a nice restaurant.
Here's what I tell my wife's family and my family. If you feel like gifting, DO NOT get us physical gifts, we don't have the space and there's a 99.99% chance you will not be right in your gift selection.
We'd love to have a call or card, but if you must spend money, gift cards to specific merchants, (insert list), or cash are acceptable.
In a conventional keyboard, the point at which the switch closes is also the point where the key bottoms out, plus or minus the amount of give that the rubber spring-membrane provides. The typing feel they provide is both impactful and gummy - you push a key until it stops abruptly, like mashing a finger down on your desk directly, and then you have to lift your finger off the key entirely to let it release. Trying to lighten the impacts can lead to missing keypresses, especially on an older keyboard.
On a mechanical keyboard (mine has Cherry MX Browns), the point at which the switches close is before the key bottoms out. Depending on the switch type, the closing point can be felt, too. They're also driven back by mechanical springs, rather than a rubber membrane. So, rather than mash the keys until they stop to guarantee a letter press, the typing feel is lighter and more controlled. It's also much bouncier, thanks to the springs - like bouncing on a trampoline, rather than trying to jump on a hard floor.
I went from old-school gummy keyboards (Yay ancient Dell hardware) to laptop-style scissors keyboards, and when my last one died, I splurged and got a mechanical keyboard instead. It's similar to a laptop-style keyboard feel, where there is a very definite point of engagement rather than tons of mush. However, the throw is still long, and the bounce-back is a new experience.
It's all about feel - definitely look around and see if you can borrow one (or multiple - there are a half-dozen different flavors of mechanical switch from Cherry alone) to try before spending the not-insignificant amount of money to buy one.
People who play games (I for one) like mechanical keyboards. I'd say the three main key switches provided by Cherry are the Cherry MX Blue, Brown, and Red, in that order from typing oriented to gaming oriented. The Blues are loud and have a clicky feel, while the Browns are quieter, but still have the clicky feel, and the Reds are simply linear switches without any sort of tactile click. I personally have browns and love them but reds are more gaming oriented, due to the lack of tactile feedback impeding the switch and the lightest force to actuate. There are several other types of Cherry switches, as well as high end options (Topre, etc. ). This was a long answer, but yes, mechanical keyboards are great for gaming as well as general use.
In the end it is just personal preference. Try it on your own and then decide. A friend of my spent a decade typing on an old mechanical IBM keyboard and then switched to a standard Apple keyboard. I am the other way around. I started with a 'soft' keyboard and now switched to a mechanical one. Both of us just prefer how the respective keyboard feels.
I think it's a good idea to give something that the person would never buy, something totally different than the things they encounter on daily basis. I got an art book once - 'woman as an inspiration', a collection of famous paintings depicting women. I loved it and I am pretty sure I would never ever buy that myself. I also love gifts that you do - I got a trip to Valencia once, that was pretty cool.
Why do we treat "hackers" as some sort of mythical beasts who belong to a whole different race altogether? Now, I'm not saying you're doing that, but this is something I've observed quite a lot. Especially with those "X for Hackers" etc..
Answering your question — it differs from person to person. I personally wouldn't be interested in receiving a new router, for example, but I do know people who would. I'd like a typewriter more, to be honest. But that's just me.
Lastly, a good gift is one that comes with sincerity. It doesn't matter what it is, as long as its sender sends along warm wishes and sincere affection.
I must second the Dremel as a good gift idea. It is the one power tool that I use weekly. Its a saw, drill, sander, and more in one. I use it for many different types of projects. Bought it in the year 2000. Its still going strong.
I got one as a gift last year. Actually, got a set of 3 tools. They have been gathering dust. I have zero skill in woodworking but am interested in learning. What do you use your Dremel for?
I really use it for everything. From home projects, to repairs, robotics, auto repair, crafts, and school projects for my child. It is a very handy tool to have. Gathering dust is not a sign of a bad tool, but a sign of a lack of projects. Go find some. :)
I don't actually have one, but I think the Silhouette allows you to convert stuff from Illustrator format. I think it also appears as a printer. So, you should be able to create cuttable content in Inkscape.
My favorite gift to receive is really just spending time with the gift giver, going out to a restaurant, maybe a show or to see a band, or a day out somewhere.
Hacker types also have a great interest in how things are made, if you can combine eating with a cooking class, or drinking with a trip to a brewery then that would work well.
Sugru (which I think is a great gift all on its own) have an alternative Christmas list here, focused on things that will last and are easily repairable, plus various other things interesting for a variety of geeky reasons.
Maybe I'm different than others here, but I would advise against software tools unless you know and understand what their actual needs/wants are. Tooling is highly personal, and they probably already have an editor they like that is fully tweaked and configured.
Hardware toys are cool (mechanical keyboards, arduino, raspberry pi, etc), as many others have said.
But you might consider meatspace items that are nice no matter who you are. I just bought a nice new smartwool hat and titanium spork (for pack lunches!) at REI for my favorite nerd.
not sure how much you want to spend, but i recently built a tube (valve) amplifier from a kit from these people http://www.bottlehead.com/ - it was about as easy as making something can be (very good instructions) and very enjoyable.
[i guess i should add that the lowest price model - the crack otl headphone amplifier - is not suitable for most headphones. so be careful before buying that one.]
Gallium is pretty nasty stuff and is much harder to clean than Mercury. Try getting a Ga droplet on your clothes; it will literally never come out. It is also a heavy metal, so it is not something you want to play around with outside of a closed jar. Its not THAT dangerous, but in the short run neither is Hg, but they are both not great long term.
Anything totally unrelated to computers, math and hacking! Food, clothing, printed books, sporting goods ... Really, seriously, us hard-core geeks have all the geeky stuff we need and want!
At the moment there are only a few very specific things which I really want or need so buying me something random will just result in wasted money on the presenters side and wasted storage space in my side. Right now I have about 15 unread books next to my bed, I have all the tools (software, mechanical/electrical tools) I will ever need, I have about 5 bicycles which I don't use and the only hobby I have right now is fitness and writing my PhD thesis.
If you want to present me something then either present me an Amazon coupon for the unlikely case that I want to order something specific in the net half year or invite me to a nice restaurant.