Heidi? Is that sort of a feminine version of SQLYog? I'll have to give it a try out. Although it would be narrow-minded of me to say I'll never switch from SQLYog, I do like to get any new ones just in case I'm missing out on something.
The man who comes back through the Door in the Wall will never be quite the same as the man who went out.
I use phpMyAdmin if it's supplied by the host, but recently started using SQL Manager Lite for MySQL for remote management of several databases. Runs from your desktop, not from the host.
(I've heard good things about HeidiSQL, but not tried it/her.)
I've recently tried DBDesigner 4 from fabforce.net for producing table schemas and ERDs, but not enough to comment fully on it, but it looks promising - it can extractand produce ERDs from an existing database for example.
I use Ross when ever possible and there are several great tools out there for mysql database administration however, I too love Navicat.
It has 3 very important features that I use all the time.
1. Data import tools for excel, cab, XML and other formats.
I never know how or where my data is going to come from when working with a flint but Nsvicat's tools give me enough options to know I'll be able to get the job done.
2. Visual sql query builder - similar to what you find in M$ Access or OOo Base.
I'm very confident with my Sql skills, but a visual query builder is just a nice tool for prototyping a complicated query quickly. You can run the query for performance testing and switch to edit the SQL code, and back,to fine tune things at any time.
3. Data Transformation Services (DTS) with option for scheduling.
When you have multiple databases DTS is a life save, pushing and pulling datasets across servers at reqular intervals if you so desire. If you've never had to do this, when you do, you'll wish you had tools like this ...
Its one of the few prices of software I happily pay for and really enjoy using.