Not so well-known games, but really good

Outland looks really cool.

Kingdoms of Amalur

Anything by Spiderweb Software.
Quite a few amazingly story rich RPGs.

Project Zombied is amazing!

Singularity. Not played myself yet, but I'm looking forward to it.

Snakes of Avalon. It's a, um, point and click adventure.
It's also free.

Harold - a endless runner platform racing game that acts like a cartoon. The visuals are amazing, the music is outstanding, and the game is frustrating, yet super fun to play.

There was a similar thread a few weeks ago, but I'll play along:

Yesterday
I Am Alive
Mars: War Logs
Fallout 2 People seem to forget that Fallout 3 had two predecessors, with 2 being the best game in the entire series

My own favourites will probably always lean towards the visual novels. Sure, I play just about every other genre of game in existence too from Solitaire to Hidden Object, FPS to Flight Simulators. But always lean towards RPGs, and in essence, visual novels are RPGs. Plus a bit of hentai on the side, depending on the novel. :P

Perhaps one that a lot of people don't realise is that a very popular anime, Clannad, started out as a visual novel. As did the Higurashi series, which we've recently seen bundled, but that's another story. There's talk of Clannad heading to steam later in the year, around November time too, so keep an eye open for that one.

But nevertheless, Clannad: The Visual Novel remains just as hilarious as the anime itself. Perhaps not quite as "sad" at a particular part of Clannad -After Story- (unless because I was already expecting it to happen) but certain scenes... Damn, I wish they'd made it to the show. Who wouldn't want to see Sunohara getting thrown across the floor by Senae, straight into the football team?!
Available in english on a number of sites, least text. No english language voiceover, unfortunately perhaps - but the Japanese voices are great too, and MANY hours worth of reading - more than most AAA titles. Each character has their own route to complete, and you even get to meet some who never appeared in the anime; and the origins of Botan. It branches off pretty early too, with plenty of twists to the "generic" story, including some "...what the hell?!" scenes with Nagisa's Dad, Akio. <3

Clannad remains one of my favourite novels and anime, but my absolute favourite novel to date is probably a mixture between two (NOTE: BOTH THE FOLLOWING ARE RATED 18+; although there are all-ages versions for both)
Hoshizora no Memoria -Wish Upon A Shooting Star- - Your atypical romance themed novel, with plenty of unusual twists, including - highly questionably, a route involving your blood sister. Though she is facepalmingly cute. She really does have demonic hands though... HOW IS IT POSSIBLE TO TURN EGGS COMPLETELY BLACK?!

Or Yumina The Ethereal a mixture visual novel and dungeon crawler. The combat does get highly repetitive and irritating though, but ultimately does unlock extra scenes is required for the "final" ending with Yumina.
Good mixture of songs in this one though.
Sample

...I could go on forever with other novels. Unless you could find the all ages version for Kira*Kira Though, whether you go 18+ or All Ages version, DO NOT TAKE KIRARI'S ROUTE LIGHTLY! Again anyway, good music, but Kirari's "normal" route messed me up more than Clannad did :P
Sample Song - Multiple "bands" in this one for different songs. One only unlocking in Kirari's normal ending.

Xpand Rally. It's criminally underrated.

Lisa:The Painful RPG

Silent Storm (and it sequel, Sentinels). Squad-based tactical RPG-ish thing with destructable terrain, set in an alternate-history WWII with some sci-fi for good measure. Think Jagged Alliance in 3D in terms of gameplay.

Go look up Jefmajor's Let's Plays of these games on Youtube. Absolutely amazing series.

Not sure if it qualifies (it has under 1,000 reviews on Steam) but Desktop Dungeons is great if you're into rogue-likes and looking for something different. It's a unique breed, like a mix of a puzzle game and board game. You start off on a board with a character at level 1. Enemies on the boards are leveled 1-10. You heal yourself and restore magic by uncovering dark/unexplored spots on the grid. As you go along you unlock new classes, areas, items, upgrades for your central town, basically tons of stuff to keep you going. I played it and FTL pretty much non-stop when my internet was out for an extended period.

And on the topic of rogue-likes, the freeware game Decker is great if you can overlook the 90s shareware graphics. Cyberpunk/hacking sort of game where you break into systems, explore nodes, and sneak past or destroy any ICE that get in your way. Heavily influenced by Neuromancer.

Where can I find out more about this Dispel game. Google gives nothing or I am searching the wrong thing.

Load up http://www.agar.io and enjoy the addiction!

Runers is a great game and there is a demo available. It's a rogue-like where you collect runes and craft spells. I'd wager that many haven't heard of it.

Full Bore. It's a nice platformer about boars. It's supposed to have a darker story, but I haven't gotten that far in it yet. It's on the Weekly Humble Bundle for a dollar.

Might & Magic: Dark Messiah

Too many to name. Literally. I've beaten so many Steam indie gems over the years that were amazing but not really well known that I could write a book about them.

Off the top of my head:

And Yet It Moves
Dust: An Elysian Tail
Blackwell Deception
One Finger Death Punch
Eternal Senia
Robot Roller-Derby Disco Dodgeball
Floating Point
RollerCoaster Tycoon (Seriously, I'm surprised at the amount of people who never played this glorious game...)

Brink of Consciousness games.
Finding Teddy.
Hamlet or the Last Game without MMORPG Features, Shaders and Product Placement (yes, that is the entire title…)
Haunted (the point 'n' click).
Jade Empire (not even some of the more hardcore BioWare fans know it even exists).
Lili: Child of Geos (super casual and repetitive, but oh so fun).
Puzzle Agent 1-2.
Poker Night at the Inventory 2.
Remember Me.
The Dark Eye: Memoria (too bad it needs Chains of Satinav to understand).
The Tiny Bang Story.
I would also say the Blackwell saga, but that ending…

Edit: And for games not on Steam:
Emperor: Rise of the Middle Kingdom – the best of the Sierra city builders, but not even GOG has it.
Oni from Bungie. My favourite brawler even to this date.

I'm surprised to see Dispel here. I very vaguely remember playing it years ago and not enjoying it much. Anyway, you can still find the game on Allegro: http://allegro.pl/dispel-pl-unikat-lodz-i5546368469.html

Here's something even more obscure: Slaterman for DOS, a very obscure platformer. I tried to look for information about this game years ago, but all I found was C64 port.