Regarding a first 18650 light, a Convoy S2+ with a modern driver is a no brainer. Cheap, robust and powerful enough for much anything. Not the shortest though. However, i do prefer the BLF A6 for it’s driver and max output. Not much more expensive if you catch a deal. No USB charging though.
Eagle eye X2R is a safe choice too. Similar tube light, moderate output with USB. Their X1R headlamp is worth looking at too.
If you can spend a little more, I’m quite impressed with the new Astrolux EC01. There is a deal going on around $25. Can’t beat the feature/price ratio.
At a slightly higher price tag but without USB, the Lumintop FW3A is a remarkable light, and the Emisar D4V2 is a little jewel that is small enough to fit in a jacket pocket - especially in 18350 configuration.
There are quite some nice Sofirm lights too, but i’m getting lost into their names an versions…
About AAA lights, i consider the Ultratac K18 one of the all time best. Small, stylish (especially the SS version) and 10440 compatible. The Lumintop Ant and Tool Ti are some of my favorites too. Jetbeam Jet µ is a reliable,twisty i would recommend too.
So many lights… you have to start somewhere but don’t need to stop there. 