I made this video because I was previously unable to find any videos like this showcasing all of the materials listed on the Valve Developer Wiki, so i went and made it myself. I hope this can help you when making your own custom textures. Enjoy!

List of Materials from the Wiki

===Special===
0:32 default
0:55 default_silent
1:14 floatingstandable
1:35 item
1:55 nodecal
2:15 player
2:55 player_control_clip

===Concrete / Rock===
3:20 boulder
3:46 brick
4:10 concrete
4:30 concrete_block
4:50 rock

===Metal===
5:10 canister
5:37 chain
6:03 chainlink
6:25 crowbar
6:45 grenade
7:13 gunship
7:40 metal
8:03 combine_metal
8:26 metal_barrel
8:50 floating_metal_barrel
9:09 metal_bouncy
9:58 Metal_box
10:19 metalgrate
10:42 metalpanel
11:01 metalvent
11:23 metalvehicle
11:45 metal_seafloorcar
12:13 slipperymetal
12:39 solidmetal
13:02 paintcan
13:31 popcan
13:49 roller
14:06 strider
14:41 weapon

===Wood===
15:05 wood
15:39 wood_Box
16:04 wood_Furniture
16:24 wood_Panel
16:47 wood_Plank
17:07 wood_Solid

===Terrain===
17:31 dirt
17:59 grass
18:20 gravel
18:43 mud
19:06 sand
19:24 quicksand
19:41 antlionsand
20:03 slipperyslime

===Liquid===
20:34 slime
21:00 water
21:29 wade

===Frozen===
21:54 ice
22:26 snow

===Organic===
22:46 watermelon
23:06 foliage
23:27 flesh
23:52 bloodyflesh
24:17 zombieflesh
24:43 alienflesh
25:06 antlion
25:27 armorflesh

===Manufactured & Misc===
25:50 glass
26:14 glassbottle
26:35 combine_glass
26:56 tile
27:15 ceiling_tile
27:38 paper
28:00 papercup
28:25 cardboard
28:46 plaster
29:11 plastic
29:35 Plastic_Box
29:58 plastic_barrel
30:20 plastic_barrel_buoyant
30:56 rubber
31:19 rubbertire
31:42 jeeptire
32:01 carpet
32:19 computer
32:39 pottery