I have a small light on my keychain, an imini 2 Rechargeable (50 lumens) now, and an i1R 2 Pro (180 lumens on high and 5 lumens on low) before that. I went from 0.78 oz down to 0.69 oz., Actually it has to be more because it's titanium instead of aluminum. Either way, you just pull the tiny light out of the magnetic base and it turns on instantly, and it turns off when you pop it back in. It can't get much more convenient than that. I have an i1R 2 EOS, 150 lumens on high and 5 on low (0.46 ounces), on my ATV key ring with the remote control for my winch and some other stuff. I have to take the ATV key off and use it by itself, because anything, even a small key fob, can turn the key off when it hits the gas tank as you move the handlebars back and forth. The other handful of stuff goes in the cargo box under the front rack.
So far I haven't used any of the keychain lights much because I usually have a bigger light in my left front pocket. Currently I have an ArkPro flashlight with a 1,500-lumen floodlight, 800-lumen spotlight, UV light, and green laser in an ArkPro holster. After carrying similar size lights in my pocket for so long, it's hard getting used to putting it back in the holster, but now I can get my hand in my pocket without taking a flashlight out first. I have an Olight flashlight in the center console of my Yukon that I can't tell you much about. It's not a catalog item and I got it on sale, on the condition I don't blab about it because it's a trial item. If I talk I may lose the privilege of being able to get trial items. It may end up being a production item, and if it does, I hope they make the change I suggested. We'll see. It it does show up as a regular thing, I'll be sure to post about it. And show what's different about mine, if anything.
I gave my friends the Olight Limited Edition Christmas Gift Box, but I don't know who gets which flashlight yet. There were only 3,000 sets made for the whole world to share. That's something like 1 for every 2.8 million people IIRC. For my friends who aren't just 1 in a million.

They made more than 3,000 of the green lights, but not the red ones or the sets they're in.