I don't think this is the right subforum for that. And your questions lacks essential info about what you're looking for. However:
You can use
Ploque Sforzando as a free alternative for Kontakt. Also from that website you can find Gbs of free sound samples with very interesting sounds.
Polyphone is a free and easy to use SF2-editor.
Also you can look for interesting software here
http://www.vst4free.com/index.php?m=Hosts&plug-ins=Host and here
https://alternativeto.net/software/lmms/