Best lens is of course dependent on a lot including what you shoot, and some of these are only available to specific mounts and in specific mounts there are many other options, but favorite? That's easy. Ignoring the CV 50 APO-Lanthar (new and suffering due to second lens choice below) and CV 50 Nokton 50 f/1 (arrived Friday, but first results are encouraging**), the clear winner is the only lens mentioned twice (different mounts), but actually three times. I bought the Voigtlander Nokton 40 f/1.2 E for a Sony system with electric coupling. Although the A7III was my least favorite camera (skin tones under mixed lighting and controls from a Fuji analog control fan), that lens-camera combo was my favorite. When I moved to the M240 I went with the 50mm VM equivalent due to frame lines with the rangefinder. And then when I traded the M240 for a SL, I re-ish bought the Nokton 40mm f/1.2, VM version this time. And of course I haven't sold any of them 'cause I'm lazy. Those Noktons are the perfect balance between character and accuracy in my book. Just pick the 40 or 50 based on FL you prefer. And don't take my word for it. Take a glance at the longest running single lens review thread over at FM (if you run through all you'll even see a birthday boy's appearance in bubble popping fun). There's an argument the Noktons are when Voigtlander went from third behind Leica and Zeiss, to equals (and of course many of Zeiss lenses are also made by Cosina, Voigtlander's owner). And if you discount the Leica approved/branded Panasonics and Zeiss approved/branded Sonys, Voigtlander has released the most lenses and experiments in the last seven or so years. Less expensive is a plus too.
Two lens prime option? A smarter person would spread out the focal lengths, but you're talking to me. I'd go for the Sigma Art 40mm f/1.4 (aka Beyond Art - one lens cine specs in a still body experiment - c'mon Sigma do it again!). The Noktons opposite. Big, heavy, 16 elements/12 groups, optically near perfect and will pull resolution out any sensor behind it. Also that auto-focus thing. And watch the pricing as it rotates mounts sales often. Currently Canon and Nikon users are in luck (Adorama a little cheaper than B&H). Check out the below video.
I love talking about camera gear and hate doing comparison shots, but you can see examples on IG and less frequently updated Flickr. Same user name and lens always mentioned in IG description at least. Using rangefinder lenses without info sent to camera doesn't help on the Flickr side and again, did I mention I'm lazy?
Ha! I'm a big believer in body-lenses combinations. Lenses are creeping up in price (approaching/matching older bodies used cost) and with sensor resolution jumps the old lens-body relationship isn't what it quite was ("date the body, marry the lenses"). If you don't mind using different systems, maybe find magic combos, instead of spreading out to all focal lengths. Or go with zooms which invalidates pretty much everything above.
Please! I'm always curious about cases/bags/straps experiences. Recently for me it's been Clever Supply straps and Stone or LATZZ drawstring bags for each lens/body and then whatever non-descript backpack my company gave me or Timbuk2 messenger bag I picked up on sale, that doesn't scream camera(s) inside.
** This is one of the 13 shots I've taken so far. Momentary Roblox disruption yesterday. Again, this is mostly family stuff so anything I say has likely zero benefit to landscape, sports, street... pretty much everything, shooters. But typing this did allow putting off cleaning house for a bit!