Solution to Killer Sudoku no 7

Solution to Killer Sudoku no 5

Solution to Killer Sudoku no 4

Here is my original version of the answer:

...and here is another from Shoshi Dembinsky, a member of the Daily Killer Sudoku group on Facebook:

Solution to Killer Sudoku no 3

Solution to Killer Sudoku no 2

Solution to Killer Sudoku no 1