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Glass Magician
EARTH
*******
spellcaster/effect
Once per turn, you may negate the activation of an opponent's spell card and return it to their hand. The opponent cannot activate it until their next turn.
2500/2000

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Glass gardna
EARTH
****
warrior/effect
Negate the effect of any trap cards tergeting your defense-position monsters and return it to the top of the owner's deck.
100/2200

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Glass dragon
EARTH
********
dragon
2800/2400

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Glass synchron
EARTH
***
machine/tuner
You may special summon this monster when an effect is negated during your turn. If this monser is special summoned this way, you may normal summon twice this turn.

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Glass Warrior
EARTH
*******
Warrior/synchro
1 "Glass" tuner + 1 or more non-tuner monsters
When this monster is synchro summoned, you may special summon as many "Glass" monsters from your graveyard as possible, with combined levels equal to or less than this monsters level. The summoned monsters are unnaffected by traps, cannot be used as synchro material monsters, and are destroyed during the end phase.
2300/1100

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Glass bug
EARTH
**
Insect/effect
When this monster is destroyed and sent to the graveyard, you may special summon 1 level 4 or lower "Glass" monster from your hand. It cannot be destroyed, until your next standby phase.

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Glass spirit
EARTH
****
Fairy/effect
As long as this card remains face-up on the field, other "Glass" monsters are unnaffected by continuous traps.
300/1700

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Glass golem
EARTH
*****
Rock/tuner
This monster is unaffected by traps. When this monster is summoned, you may discard up to 2 cards from your hand. For each card discarded, special summon 1 "Glass shard token"(EARTH/rock/level 1/0 ATK/0 DEF). These tokens are destroyed during the end phase.
2000/400

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Glass idol
EARTH
**
rock/effect
During your main phase, you may tribute this card to destroy spells/traps on the field equal to the number of your standby pahses this card has been face-up on your side of the field.

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Glass bird
EARTH
***
winged-beast/effect
Once per turn, you may return 1 "Glass" monster on your side of the field to your hand to reveal all face-down cards your opponent controls.
1300/600

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Glass worker
EARTH
***
warrior/effect
Once per turn, you can pay 500 LP to make 1 "glass" monster on your side of the field unable to be destroyed by battle (damage calculation is applied normally)
600/0

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Obsidian knight
EARTH
**********
Ritual/effect
This card can only be ritual summoned with "Black glass ritual". Once per turn, you can send one "Glass" monster from your deck to the graveyard, to halve the attack of all level 5 or higher monsters your opponent controls, until the end phase.
2600/2000

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Glass recycling
Spell
Return up to 3 "Glass" monsters from your graveyard to your deck. Your deck is then shuffled.

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Glass factory
Field spell
Every time a "Glass" monster is destroyed and sent to the graveyard, place 1 "broken glass counter" on this card. Once per turn, during your main phase, you can remove "broken glass counter"s from this csrd to special summon 1 "Glass" monster from your graveyard or hand with a level equal to the number of "broken glass counter"s removed.

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Glass infusion
Equip spell
Equip this only to a "Glass" monster you control. It cannot be removed from the field by the effects of spell cards. When this card is removed from the field, destroy the equiped monster.

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Glass Grenade
Trap
Tribute 1 "Glass" monster you control. Destroy 1 card on your opponent's side of the field.

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Marble launch
quick-play spell
This card can only be activated during your turn. Select 1 level 4 or lower "Glass" monster you control. It may attack directly this turn.

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Stained glass
Continuous spell
Negate the effects of all "Glass" monsters on the field, and raise their attack by 400.

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Glass monolith
counter trap
This card can only be activated in respinse to a spell or trap your opponent activates. The effect of the card becomes "your opponent must reveal their hand. Select 1 card and place it at the bottom of their deck."

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Blown glass
quick-play spell
Increase the attack of all "Glass" monsters on the field by 300, and decrease their defense by 500, until the end phase of the turn this card is activated.

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Black glass ritual
ritual spell
Offer monsters on your side of the field or in your hand whose total levels are equal to or are greater than 10. Special summon 1 "Obsidian kinght" from your hand. If an "Obsidian knight" on your side of the field would be destroyed, you can remove this card in your graveyard from play, and "Obsidian knight" will not be destroyed (damage calculation is applied normally)

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Glass mirror
spell
Select 1 "Glass" monster you control. Special summon 1 "reflection token" with the same ATK, DEF, level, type, and attribute on your side of the field. If the original monster would be removed from the field by a card effect, you may destroy the "reflection token" instead.

It is indeed, and it was really quite useful in the old DARK decks: http://yugioh.wikia.com/wiki/Obsidian_Dragon

Also, I can see Glass Warrior being horribly, horribly abused. "Glass Synchron and Glass Gardna for Glass Warrior, bring back Glass Synchron and Glass Gardna for Glass Warrior, bring back Glass Synchron and Glass Gardna for Glass Warrior, bring back Glass Synchron and Glass Gardna for any other Level 7 synchro."

If I may add another:

Glass Desert Sunlight
Normal Trap
Activate when your opponent activates a spell, trap, or an effect of an effect monster during their main phase while you control a "Glass" monster. Once that effect resolves, neither player can activate spells, traps, or effect monster's effects until the end of this turn. Your opponent skips their battle phase.

Gah, that's over powered by miles.