The top of my dashboard
I really like the breeze dark theme.
I HIGHLY recommend configuring the Ultimate Timeline to show reviews by SRS level out to 120 days. Shows you at a glance if you’re maintaining a pretty even workload or if you have managed to clump up your reviews. (I’ve expanded this for the screenshot, but I usually keep it folded up to save screen real-estate since I’ve managed to keep a consistent pace for many, many months now.)
The Heatmap userscript is also de rigueur in my book.
The Item Inspector is a terrific swiss army knife for figuring out what’s in your history and queue.
Finally, I’m a big fan of the ganbarometer and burn progress scripts for some odd reason. As simple as the latter is, it’s quite satisfying to see those golden bars gradually move to the right (it was the first user script I ever wrote).
Other non-dashboard scripts I use
IME2Furigana for this discourse forum (quirky, but incredibly useful for adding furigana to forum posts).
The Niai, Confusion Guesser, and Keisei scripts as mentioned are also extremely valuable during reviews.
I also recommend the simple Hide Context Sentence script and the Unobtrusive Stroke Order scripts.
I find the Wanikani Spacebar Expand All script mandatory to work around a bug with the new lesson layouts.
Finally, the WKstats projection page script is a nice plugin for the wkstats site (helps me project whether I’ll really get to 60 before Christmas or not 
).