In no particular order:
1. A friend recently got a new phone & number on Verizon, and neglected to set up his electronic voicemail account for the first few weeks. When you call, after 4-5 rings it goes to voicemail but the message is simply "This user has not set up their voicemail yet. Goodbye."
Now, this won't work for everyone, but if you spend a minimal amount of time being interrupted by phone calls and you have a stable job and relationships and don't need to get every single call that comes in, this no-voicemail thing is kind of awesome because it is one less inbox for this friend's life. I know when I get that message I'll either text, call back later, or just send an email. I'm envious and may not set up voicemail for future new phones I get.
2. In the spirit of Last Year's Model, my home landline is connected to a 11 year-old cordless phone we have no reason to replace. It works for the hour or so total talk time we use it each week, but since the phone sits in the cradle charging constantly, the batteries tend to go bad after a few years. The batteries are currently dying so the phone has to stay on the charger all the time, and when you do get a call, you get about 10 minutes of talk time before the batteries are dead and the call drops.
Instead of replacing the rechargable battery pack, I've been enjoying this feature for a few months now. I know it's kind of asshole-ish, but it's really nice to be able to keep things short and sweet with everyone that calls my house. It's really handy and I don't spend hours on the phone chit-chatting because the phone simply can't do it, and I have no guilt about cutting a call short. I can always have a long conversation on my cell phone if need be.
3. There are several web services out there to answer the question "Who owns that unlisted number that just hit my mobile phone?" but my favorite is WhoCalled.Us. It's an awesome free service where people report details of who called them and what they wanted when they called, think of it as crowd-sourced telemarketer reporting. It's handy because you can safely ignore most calls to your phone after looking up the numbers at this site.
If a weird unknown number comes into my iPhone, I ignore it and look up the number later. 9 times out of 10, it was a sales call from a bank, a timeshare company, or a bullshit work-at-home offer. I wish it was integrated in my phone, so I could just hit a button to do auto lookups from the missed calls page on my phone, or if an incoming call had known records at whocalled.us, it could display the top three rated comments on my screen before I hit accept or reject.
(this post was also translated into the Czech language)