I agree with Leren. HoDoKu has an excellent interface and it has many options that enhance learning methods. The developer of HoDoKu is Bernhard Hobiger. The last release was back in 2012. To my knowledge, HoDoKu is still the only solver to include the various advanced forms of Kraken Fish. It does not include Exocets, SK Loops or MSLSs.
Philip Beeby's solver 'Phil's Folly' is also excellent. This solver does include SK Loops [including some extended versions], MSLSs and MultiFish and Kraken Units [labelled Forcing Chains]. Phil's Folly does include some the strategies associated with Exocets [but not all].
Andrew Stuart's solver includes a solution count tool and a set of options to add strong links to the puzzle. Andrew recently added a number of Exocet moves. This solver includes Aligned Pair Exclusion, WXYZ and Death Blossom.
Both Philip and Andrew are continuing to revise and update their solvers.
No one has yet implemented all of the methods in David P. Bird's excellent compendium on Junior Exocet [JE]. That would be quite a daunting task.
www.philsfolly.net.auwww.sudokuwiki.org/sudoku.htmAlso:
Nicolas Juillerat's Sudoku Explainer is still highly regarded; particularly for its rating of the difficulty of puzzles. I believe the last release of this solver was in 2007.
Allan Barker's XSUDO is highly unusual and I believe it is very powerful. This solver offers 3D images of moves and has a very distinctive set of namings of methods. This solver was last updated in 2010.
Glenn Fowler's gsf solver/creator is often cited as an excellent tool for puzzle creation in addition to its solving facility.
A person who prefers to be known as StrmCkr is developing a very comprehensive solver, stormduko, that, in particular, expands the WXYZ Wing methods
diuf.unifr.ch/pai/people/juillera/Sudoku/Sudoku.html
sudokuone.com/
gsf.cococlyde.org/download/sudoku
forum.enjoysudoku.com/stormduko-t32977.html
Solvers that merely display the solution [without displaying solution paths] are of limited utility imho. Perhaps, I have missed other worthy solvers though.
Best
Gordon