Suggest me small games (Mb wise) which are good

How small? Under 100MB, under 1GB, under 5GB?
First ideas:
Terraria 100MB
Risk of Rain 104MB
Hammerwatch 242MB

FTL about 200MB

Iron Snout.

Rogue Legacy, Fez, LOTS of VN's....

Games under 500 MB:
Mini Metro 258MB
Waves 188MB
One More Line 333MB
Alchemist's Awakening 289MB
Super Sanctum TD 112MB
Super Meat Boy 262MB
Scoregasm 67MB
One Finger Death Punch 221MB

Boson X - 12MB
Light - 486MB
LYNE - 64MB
Race the Sun - 147MB
VVVVVV - 64MB

Almost all Visual Novels, but i'm not sure if you like this genre.

The DOOM series, less than 45 MB each
Ultimate DOOM
DOOM II
Final DOOM
Fortix 113 MB
Geneforge 1 41 MB
Jamestown 210 MB
Lone Survivor 132 MB
MURI 3 MB
Noitu Love 2: Devolution 12 MB
Steamworld Dig 192 MB
Unity of Command 269 MB
Commander Keen 25 MB (for all the games together)
Dungeons of Dredmor 262 MB

SpaceChem Lots of puzzles, ~280 MB

There's a free demo too that probably even smaller but still enough puzzles to last an hour or two.

Flamebreak is still on sale for $4.99 (50%) right now; I've had a ton of fun with it so far. It's a top-down roguelike similar to Binding of Isaac, but with some MOBA-like aspects, particularly regarding your attacks and skills. It takes up 303MB on my hard drive. Definitely worth checking out. http://store.steampowered.com/app/399640/

Shovel Knight is also a great game. One of the best NES-style platformers out there, and it only takes up 268MB. One thing I like about it is that not only do you get the main campaign, but they put in a free update where you can play a separate campaign as one of the bosses, Plague Knight. I think this one should be part of everyone's collection. http://store.steampowered.com/app/250760/

Pixel Dungeon 124MB

the book of legends 132MB
downwell 32MB
the dweller 18MB
faerie solitaire 98MB
faeverse alchemy 80MB
unium 46MB
vox populi vox dei2 147MB
no thing 109MB
love 177MB

Most any RPGMaker titles.

nuclear throne
duke nuken 3D
sword of the stars: the pit
sometimes always monsters

Defender's Quest: Valley of forgotten. (Well I think it was small MB-wise)
Super meat boy is probably a bit larger. Both great games for sure.

Rogue Legacy and Risk of Rain were already mentioned. FTL too if you are a tactical lover. All 3 amazing. Retro goodness.

Factorio 360MB
It's a little bigger than most of these, but it's one of my favorite games so I just had to recommend it.
FTL 175MB
It's also a really good game.

VVVVVV (69MB)

Super Hexagon (32MB)

Angry Video Game Nerd Adventures (135MB)

Check out the front page of gamejolt,really.

Chains 30MB puzzle game with many different levels

RUSH ~400MB puzzle game with many cubes

TOME ~500MB rpg-roguelike with many unlockables and tactics. You may need to google some tricks on more then normal difficulty.

Switchcars 34 mb
Bit Blaster XL 183 mb

To the moon 100mb
A bird story 200 mb
Garden rescue christmas edition 160 mb I think the non christmas is about the same
Dwarfs!? 367 mb part of the game is FTP
Sparkle 2 evo 180MB
Z 387 MB
Hexcels series ranges from 64 to 99 mb
Hook 55 mb
others already mentioned LYNE