On most cars I've had (in modern time) the driver's window control is labeled "Auto" -- that is if the driver presses down, or up and holds for an extra second, the window goes all the way down, or all the way up. It is still possible to go down a little, and release the control, but very easy to get the window all the way down (or up) with one 'command.' Interesting to note on the Clarity, all of the windows including the rear ones work this way, at least on the drivers console. So if you want to quickly and easily open one or more windows it's easy to do-- even "manually." And of course, as others have mentioned unlock, then unlock hold puts all the windows down (on the FOB).
And not really hidden but worth a mention. Clarity supports walk-away auto-lock which I love and use every day. It's the only way I ever lock the car, and it works flawlessly for me. (I realize some in these forums have not had this experience). I'm not exaggerating when I say I've almost never manually lock the car, unless I hear rapid beeps which is extremely rare. The rapid beeps mean the car was unable to auto-lock. Anyway, it's also not included on modern Toyota competitors -- say Highlander even with Toyota Sense 2.0. There's no walk away auto-lock.
One can tune when and if the car auto-locks doors. Further, it's tunable how many doors unlock too. So for me, unlock always means all 4 doors, but the setting is adjustable. I also don't permit the car to auto-lock doors ever (no young kids to worry about opening a door).
Wipers auto-adjust speed of wiping by your cars speed. I find this one cool but some may find odd.
The auto-on for the headlights is adjustable. So if you desire headlights to turn on automatically at dusk, easy to tune that setting. Also if you prefer they don't turn on easily, easy to tune that setting.
Simply turning the car off, sets parking. i.e. never a need to press P first.
Sport mode- in my opinion just turn it on and leave it on all the time. That coupled with max regen all of the time makes for nearly one peddle driving (as KentuckyKen taught me)
No way unique but adaptive cruise control with low-speed follow is awesome. I use it a lot, but its a godsend on long drives.
The rear seat has a pull down drink holder. Again not unique at all but may be "hidden"
My favorite feature I use all summer long is turning on air conditioning without making any engine sound or exhaust. If stuck waiting in a hot parking lot, no one knows my AC is turned on but me. Also remote climate control is super-useful.