I've got a list of "While Whale" games that I always have the itch for, but I'm either the Forever GM or games fall through IRL/Online before they ever really get going.
L5R 4e. I just love everything about L5R in general, but the ruleset by FFG -- like their other products -- just don't grok with me for some reason. I've been in a few online Winter Court-esque games, but they're always so abundantly overcrowded I find it's hard for anyone except the vets who've been there since Day 1 to really get a chance to shine.
Shadow of the Demon Lord. I just recently finished a long campaign of this with a pretty bitter-sweet ending, and I'd love to actually get to play it for a chance. The grim darkness of this distant fantasy world, however, doesn't seem terribly popular. Sad face.
Ryuutama & Golden Sky Stories. These two are technically unrelated, but they're similar thematically in many ways and also the two I've probably had my eye on for the longest time. I've been dying to really get into a game for Ryuutama in particular. I'm a huge Dragon Quest/Studio Ghibli nerd, and both of these games tick all the boxes for me. I've run a one-shot of Ryuutama, but the curse of Forever GM knows no bounds, haha.
The Final Girl. Admittedly, I get to play this one once or twice a year. It's a game I thought I'd hate, but fell in love with. Big groups, small groups, doesn't matter; it's so light weight you can barrel through an entire "campaign"/film in the span of a few hours. It's fast and visceral, and being the B-Grade horror fan that I am, I love everything about the stereotypical slasher flick scenario in RPG format. Also helps that all you need is some imagination, some index cards and a deck of playing cards.
Masks. I backed this game way back when. I've yet to even play it, try as I might to convince my regular group to give it a shot. Makes me sad every time I see the book on my shelf collecting dust, but hey, it sure is nice to flip through from time to time :D