1) There are lots of things that do this. But over the years, I have settled on a Nmap as the gold standard to do this reliably and thoroughly. Nmap is a very powerful tool that can do a whole host of things, and it is worth it to use it for simpler stuff so you can start learning it.
Nmap is free and open source. Nmap
It has a GUI, and from the GUI (or the command line too) you can run this command to run a ping scan:
nmap -sn -oG Afilewiththepingresults.txt 192.168.1.1-255
That gives you everything on the subnet and it writes it to a file. (It will also show you the results in the GUI too.)
2) There is another "single purpose" scanner that I recommend that has a smaller footprint but it too is open source and free. Pretty slick. Angry IP Scanner
3) When I find myself connected to a network wirelessly using my android phone I very happy with Fing Network Tools.