Most of the tools were asking me to sign up, some of them allowed me to open CSV but then came a big popup asking for my credit card so that I can edit it or use some filters, and lot of them were sending CSV to server in case it was large. I will be honest, there were some which were no signup or no server, but their UX was bad - sublime was showing the content better than those.
Then I started building one for myself, and it turns out building no signup, browser only CSV tool is actually possible even for managing large CSVs; I was able to make it up and running within days and it turns out to be awesome - apologies for shameless bragging.
Later I added support for downloading content in JSON and other alternatives of CSV like PSV, TSV, SSV, etc. It has all the basic functionalities for working with CSVs - filtering, sorting, editing, deleting, downloading in your desired format.
In near future, I am planning to make it one shot CSV editor for all kinds of platform - browser extensions, desktop app and hopefully mobile apps too ( I am bad at building mobile apps, but I will try my best ). Do check it out and let me know in comments, what you feel about it.