I’ll start.
Based on time, I use Aux LEDs most because they are always on (red and blue on low).
Next is a combo of hold for low, then ramp up (and sometimes down a little), to off. This is usually while I’m working.
Lastly, double click to high for a short while, then off. This is to momentarily light up an entire room or safely see the delivery person to their vehicle.
What are your most used Andúril features / modes?
The ramping,
Memory,
Aux leds for voltage indication,
double for turbo,
lightning mode to impress muggles 
Not counting basic functions (aux leds, ramping and shortcuts) I use the two step lockout, the bike flasher when walking the dogs on the road at night and I use the programmable ramp floor / ceiling to make the light act as a single mode max only (by setting the ramp floor to 150)
Manual memory (set to first blink mark). Very nice feature. But my D4V2 has been most of its life in candle-mode 
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Ramping up or down upon turning on, and ramping up or down while already on.
ramping - usually continuous mode, but now and then i switch to levels
memory i guess
voltage check
next i would like muggle mode but it doesn;t really work on early version
-i would also like muggle mode to be more like regular mode (the ramping UI is somewhat different) but TK said that wasn;t the intent
moonlight mode i guess, is that a feature? i just have it on the minimum allowed
i have the max mode set below the real max, i guess that is a feature
sometimes i will double click from off, for a bright blast
never bike blinker, temp check, nightlight mode, candle mode, lightning mode, lockout, emerg slow flasher,
what would i wish it did not do: not much i guess, oh wait - i don;t like the blink when it switches driver modes - i just dont; care
it seems like a bug every time i notice it
Variable strobe is funny with fans.
I don’t, my anduril lights sit on a shelf… if/when I do use/play with them… ramping… I prefer PB lights to EDC…
ON and OFF for sure.
1. On/Off
2. Click Hold to start in lowest
3. Ramping
4. Electronic Lockout (4clicks)
a. Momentary
I really like the easy lock-out, of course ramping …and other than that the candle mode.
Only my SP36es are running Andouille, and the rest are Narsim, Bistro, and proprietary UIs (Sofirn, Nitecore, etc.).
So… on/off and ramp up/down. Mostly.
Ramping
TURBO
AUX, various settings for different lights, scenarios, locked/unlocked.
Lockout+momentary+L2
Batt check
All my lights on lightning mode when I’m on a social video conference
I’ll dissent from the majority so far in that I use stepped mode. I also use the two level lockout momentary, shortcuts to moonlight/high/turbo, candle/lightning modes, aux settings, battery check… I love Anduril. 
I love that super smooth and pretty linear looking ramp. Just fast enough, perfect for a quick fix. I really wish my D10 would ramp so well. It delays way too long then suddenly starts slow aaaand it’s all gone. Besides an SST-20 swap I would really love Anduril on it.
I currently have two "Lumintop EDC18" and two "Sofirn SP36" Andúril" lights and are awaiting the arrival of one "Sofirn BLF LT1" lantern.
I mostly just use the basic on/off, brightness ramping, direct to moonlight and access to turbo features but would not want to give up any of the other features.
A very useful feature in Andúril is the (three clicks from off) "battery voltage blink-out".
An important safety feature in Andúril is the (built-in) "low voltage battery protection".
I also appreciate "Muggle Mode" (for when I lend any Andúril light to someone else) and Andúril's temperature readout with calibration setting along with the built-in temperature regulation.
It did take an attitude adjustment having to memorize an instruction manual instead of just experimenting to understand the entire Andúril user interface. I generally prefer items which are elegant and simple ("simply elegant" and "elegantly simple") but that will not stop me from purchasing another Andúril light and it does seem simpler the more I use it and if I use it often enough.
I like, and use ramping, the most.
On/Off
Ramping
Direct to Low
Direct to High
Candlelight (I LOVE this with a 3000k light! - Use it every night, in the bedroom.)
Battery Level check.
I love this User Interface. Cheers, ToyKeeper!