Thinko! is a unique blend of many types of brain exercises. 

Online Thinko! has sudoku, word searches, crosswords and trivia.

Thinko! Games has trivia, multiple choice questions, word search, drawing, tongue twisters, spatial awareness questions, memory games and aeronautical engineering (aka paper aeroplane design).

Thinko! Trivia has trivia, multiple choice questions, a paper aeroplane challenge and a range of other challenges to choose from.