Traditional, abstract, strategic, open-source games

Backgammon
Checkers
Chess
Connect Four
Crazy Eights
Dominoes
Dots and Boxes
Go Fish
Gin Rummy
Hearts
Nine Men's Morris
Poker
Solitaire
Spades
Tabla Lusoria
Tic Tac Toe

Unicode Characters for an Updated Nethack

Terrain

U+2668 HOT SPRINGS
U+2312 ARC looks like a hill
U+2248 ALMOST EQUAL TO rough water

Structures
U+2500 -- U+257F BOX DRAWING drawing walls and buildings
U+2302 HOUSE
U+265C BLACK CHESS ROOK could be a tower
U+271D CROSS or U+2671 EAST SYRIAC CROSS could represent a church or be a cross

Other cool things

U+2680 -- U+2685 DIE FACE roll them dice
U+231A WATCH
U+231B HOURGLASS
U+2744 SNOWFLAKE
U+2614 UMBRELLA WITH RAIN DROPS
U+2615 HOT BEVERAGE
U+263C WHITE SUN WITH RAYS
U+2388 HELM SYMBOL avast ye land lubbers
U+2639 WHITE FROWNING FACE
U+263A WHITE SMILING FACE have a nice day
U+2690 WHITE FLAG
U+2691 BLACK FLAG
U+2692 HAMMER AND PICK
U+2693 ANCHOR harbor (on maps)
U+2694 CROSSED SWORDS battleground (on maps)
U+2695 STAFF OF AESCULAPIUS medicine
U+2696 SCALES jurisprudence
U+2697 ALEMBIC chemistry
U+2698 FLOWER
U+2699 GEAR technology, tools
U+269A STAFF OF HERMES commerce