House Rules: Other Ways To Play
Gestalt - (WotC design - Unearthed Arcana) Characters play as two classes as opposed to one, taking the best benefits of each class as they level.
It's You, Not Your Equipment - (WotC design, wizards.com) Characters are not permitted to ever purchase magic items that provide an enhancement bonus to ability scores (ex: periapt of wisdom, cloak of charisma, etc), and the characters start with 10-15% less gold than the normal starting gold for their level. However, in exchange, they gain a feat every odd level, and an ability point increase every even level in place of the normal rates.
Expanded Threshhold - (WotC design, Epic Level Handbook) Usually, characters are considered dead at -10 hit points (HP) unless affected by a spell or feat. With this house rule, once passing level 10, the character can sustain negative HP damage equal to their level before dying (ex: A level 15 character will be dead at -15 HP.)