Web Based Tools

Workbench

The one and only tool that everyone should know. If you don't know it, start learning it. It is just the baseline of everything.

https://workbench.developerforce.com/login.php?startUrl=%2Fquery.php

CloudToolKit

Is actually 8 tools - Best practices analyzer, Org Compare tool, Data Compare tool, Schema Lister, Field Creator and validation/trigger switcher

https://cloudtoolkit.co/

Profile Power Tools - Mass edit profiles

Literally does what it tells you. Allows you to mass edit profiles.

https://profilepowertools.com

Google for salesforce - Search the web and only get Salesforce related results

Avoids you having to applya gazillion filters when doing your Google searches.

 https://sfdcsearch.com/

Json 2 apex - Create Apex based on your jason

http://json2apex.herokuapp.com/

Cert Score Calculator 

https://scuvanov.github.io/SalesforceCertScoreCalculator/

Permissions Comparison

https://perm-comparator.herokuapp.com/

Event Log Viewer

https://salesforce-elf.herokuapp.com/

DbDiagram

https://dbdiagram.io

If you use Lucidchart to genarate your Entity Diagrams you should switch over to this. When you're done with LucidChart, what you have is an image.That work is lost. If you use DbDiagram or equivalent, you just write JSON, which you then can reuse to actually create your fields etc.

QueryBuilder

https://querybuilder9000.herokuapp.com/

Doing SOQL queries that can be comre complex than reports, but without the hassle, since... a few years now ? no idea.