Honestly, I don't really have grails. If there's a light I see that I want bad enough, I hustle until I make it happen.
My best light, or the one I'm most proud of that I had to hustle to get is, first and foremost, my Sigma Damascus Copperhead Regulus. Man did I sell to get that one. Sold knives, lights, iirc I sold a McGizmo Mule, an Okluma, and a knife to be able to get it. No regrets, I ended up rebuying a different Okluma (or two), and a Haiku.
My HDS Action light wasn't terribly expensive but I don't think I'll ever part with that one. Spy 005 in black Al and chrome with a warm emitter swap by lazer is also irreplaceable and much beloved.
I hope to one day be lucky enough to own one of the older Spy 007 and there's a dude on Instagram that made a flashlight for himself, every time he posts it I envy him.
I was lucky enough to score a brass Hanko Trident which should have been my grail. Now my ultimate grail is a Mokume Trident and/or any of the older ones with teardrop head. I still want the one from Instagram (maker is Maverick). Not to into the 007 anymore but the Trek with a clip looks great. Any of LM Toolworks band engraved lights are grail worthy too, I’m lucky to have one. HDS thrower head is on my list, as is an 85tr if I find one at a good price. Tim Miklos’ work is up there too, and a McGizmo Lunasol. Crap, it seems my list grew instead of shrunk