Looking for more avant garde or high quality indie games, any suggestions?

So far I'd list Monument Valley, Blek, FTL, A Dark Room, The Room 1 & 2, Kairo, Superbrothers, Year Walk, Device 6, Terraria as some that I consider high quality indie.

Anyone have any more recommendations?

Oceanhorn
EPOCH 1 & 2
VVVVVV
Polara
Adventure Beaks
Limbo
Heroes & Castles
Bug Heroes 2
Shellrazer
Wayward Souls
Shardlands
Battleheart
Battleheart Legacy
Boson X
Swordigo
Indigo Lake
Slayin
Phoenix HD
Danmaku Unlimited 2
Sky Force 2014
Unmechanical
Invader Hunter

2-bit Cowboy
Blade Dash
Bloo Kid 2
Commander Pixman
Dokuro
Kung Fu Quest - The Jade Tower

Wimp: who stole my pants
Incoboto
Bastion

Twined is fun, it was a free s few days ago, dunno if it's gone back up yet.
Badlands is one of my faves too.

World of Goo

I second this. I got it on PC when it first came out. It can get tough as nails in the later parts, but it's a really fun game.

As for more suggestions, I love lone wolf. It's half adventure book, half turn based/action rpg. It's got a season pass for around 15 dollars I'd say, maybe a bit more. Dungeonism is a pretty simple but very fun dungeon crawling, semi rogue like. Lots of content. Castle Doombad isn't easy, but it's a fun kind of tower defense game. Hope I helped

Ridiculous fishing
Badland
Wayward Souls
Leo's Fortune
Darkin
Finding Teddy
Deep Dungeons of Doom
Kelly
iDagger
Wave Trip
Super Hexagon
Mage Gaunlet
1001 Attempst
Threes!

Ephemerid