A question like this is very subjective. Everyone buys and uses what works best for them.
For me:
Primary development is done on a recent 13 inch Macbook Pro. I was a long time Windows user and since I switched almost 10 years ago, I haven't been able to go back. With the *bsd base system of OS X, it's hard to beat it. OS X isn't without it's flaws and I feel it's pretty flawed from a programmers point of view now a days, but it's my preferred machine / os.
I had a 15 inch Macbook Pro before and long story short, got the 13 about a year ago. Got the 15 fixed and gave it to the wife. Every time I go to use her 15, I'm amazed at how much heavier it is. If your don't need the bigger screen, the 13 MBP is nice.
The 13 is pretty light so I don't carry it in a laptop bag often, but when I do, I use a probably 6 year old now Oakley laptop bag. Best bag I've ever owned. Easily caries 3 laptops, network tools, etc... Plenty of padding to keep it safe on a plane or being dropped "by accident"
I recently got a 32 inch Dell IPS curved monitor - it's great but I hate being tied to a desk when working at home so it gets used when I have "serious, get this stuff done, right now" work to do.
I'm waiting on a standing desk to be delivered from https://www.autonomous.ai/desk (everything is on back order :( ) - Will probably use the IPS more when that comes.
I keep an iPad 3 retina around for testing; have an iPad Pro w/ Pencil for random mockups / testing and an Android tablet cause I got it for free. I also keep a few Windows laptops with Windows XP, 7 and 8 on them around for IE testing. I have a subscription to browserstack.com and it's good enough that I feel I won't refresh any of the PC laptops as they age.
I'm a fan of Sublime Text and Transmit for editor / sftp. Pixelmator and the like are great if your trying to save a buck or 2, but I prefer Adobe CC and use Photoshop / Illustrator often. Find someone with a student discount and save a bit on Adobe CC.
Mix of Dropbox and iCloud for storing files when I won't be near my Time Capsule and a subscription to Apple Music because what programmer works without music?!?
I carry an iPhone 6s because I think the plus is to big and an Apple Watch attempts to keep me distraction free. 'Been an iPhone user since day 1 so no chance of switching to Android for the sake of loosing everything I've purchased over the last decade. Both will get upgraded when new ones come out (YAY T-Mobile Jump On Demand!)