SpeQ Mathematics - SpeQ is a small, extensive mathematics program with a simple, intuitive interface.
Tipping - Ridiculously quick tip calculator
Qalculate! - Qalculate! is a multiplatform multi-purpose desktop calculator.
Calcbot for Apple Watch - Calculate, convert, and split tips from your wrist
NoteCalc - Browser-based notepad built for math calculations.
Toothpick - Calculate your tip based on the server's gender