Here's a five player idea that I just came up with:
ELEMENTAL MAFIAThere are five players and five roles secretly assigned: fire, air, water, earth and wood. Each element is allied with two other elements and is enemy with two other elements. A player wins when both their enemies are dead. The allegiances are as you'd expect:
Fire is allied with Air and Earth, enemy to Water and Wood.
Air is allied with Fire and Water, enemy to Earth and Wood.
Water is allied with Air and Wood, enemy to Fire and Earth.
Wood is allied with Water and Earth, enemy to Air and Fire.
Earth is allied with Wood and Fire, enemy to Water and Air.
Each day each player must choose to Lynch one other player and also Protect one other player (not themselves). These actions are performed publicly, no PMing is allowed. This encourages the players to spend their time seeking alliances. The day ends when ALL the players have assigned both an attacking and a defending action, and one person has more kills-minus-protects against them than any other player. You only find out what element another player is after they've been killed.
If everyone is uninformed, the game might be too random. Two possible solutions: either each player randomly knows the identity of one other player (thus sparking in-game analysis of what knowledge a person's lynch and protect votes might indicate); or each element has a secret power; or both.
Possible powers:
Water: has an additional optional protect vote
Fire: has an additional optional lynch vote
Air: Each day can secretly detect the role of one other player
Earth: Can self-protect
Wood: If the above players powers can be done secretly via PM, then perhaps wood's power is that it can mimic any of the other's powers but they must do it publicly.