For me, that would be Secure CRT. I have yet to find a terminal emulator that matches its feature set. If you regularly manage hundreds of machines using various connection protocols (serial and ssh mostly in my case) It’s worth the $$$, and so far there hasn’t been any subscription nonsense. I liked using it at work so much I forked over the dough to have it at home.
None of the free alternatives do everything I need.
I’ll also mention a few iOS apps. One is Sun Surveyor. It’s an AR app that shows you the position of the sun, moon, and galactic center at any given time. The other would have to be Radarscope. It’s a weather radar app, but it’s a really good weather radar app.
I paid for a copy of the Torque app on android. It lets you use bluetooth OBD2 adapters to connect to your car’s ECU for reading live engine data and trouble codes. The pro paid version unlocks a lot more customization for data logging screens, allows you to save live data logs to your phone, and enables a wider range of readable codes… Makes a huge difference diagnosing weird engine issues in cars 1996 and newer.
Used the free version, don’t know why I updated to paid, WORTH IT ($5). I’ll never not have a BT adapter ($4) on my car computer and Torque on hand. Worth it just to read check engine lights.
Wife’s car occasionally throws, and sometimes clears, a minor emissions error, kills the cruise control. The passenger can reset it rolling down the interstate and we’re back in business.
I paid for a license of obd jscan for my vehicle since it is specific to Dodge/Jeep it can do everything, including activation of features and access to all data in the vehicle. I had to buy a more expensive vlink adapter, but it was only $20 or so. It has saved me tons of money so far. I was able to program keys, activate remote start (had to install a hood switch), and have been able to diagnose several issues with things like tpms and abs.
+1 for Torque, pay once and it does exactly what it’s supposed to do and doesn’t bother you with anything else.