If you want a challenging strategy game for up to 4 players, then Blokus Trigon is a great choice. 

It's an exciting game which has simple rules but offers an infinite number of combinations on a unique hexagonal playing board. Up to four players use different coloured and shaped pieces to try and fill as many places on the board as they can.

Strategy is important and the only rule is that your piece must touch one of your other pieces at the corners - and only the corners! But with Trigon there is a variation - a corner can now touch an edge, creating a whole new world of strategy and options. So with Trigon, the one rule is now that pieces cannot touch along an edge.

It's recommended for ages 8 and up.  The original Blokus game was awarded Game of the Year in 2004 and Bronze as Toy of the Year in 2005.