ANTS Profiler. I haven't used many, but I don't really have any complaints about ANTS. The visualization is really helpful.
Haven't tried it myself, but maybe dotTrace? Their ReSharper application is certainly a good one. Maybe dotTrace is too :)
Others have covered performance profiling, but with regards to memory profiling I'm currently evaluating both the Scitech .NET Memory Profiler 3.1 and ANTS Memory Profiler 5.1 (current versions as of September 2009). I tried the JetBrains one a year or two ago and it wasn't as good as ANTS (for memory profiling) so I haven't bothered this time. From reading the web sites it looks like it doesn't have the same memory profiling features as the other two.
Both ANTS and the Scitech memory profiler have features that the other doesn't, so which is best will depend upon your preferences. Generally speaking, the Scitech one provides more detailed information while the ANTS one is really incredible at identifying the leaking object. Overall, I prefer the ANTS one because it is so quick at identifying possible leaks.
Here are the main the pros and cons of each from my experience:
Common Features of ANTS and Scitech .NET Memory Profiler
Scitech .NET Memory Profiler
By way of summary, I think ANTS helps you find what's leaking faster while Scitech provides a bit more detail about your overall application memory performance and individual objects once you know what to look at (eg. stack trace on creation). If the stack trace and tracking of undisposed disposable objects was added to ANTS I wouldn't see the need to use anything else.
The current release of SharpDevelop (3.1.1) has a nice integrated profiler. It's quite fast, and integrates very well into the SharpDevelop IDE and its NUnit runner. Results are displayed in a flexible Tree/List style (use LINQ to create your own selection). Doubleclicking the displayed method jumps directly into the source code.
AQTime is reasonable, but has a bit of a learning curve and isn't as easy to use as the built in one in Team Suite
I would like to add yourkit java and .net profiler, I love it for Java, haven't tried .NET version though.
Unfortunate most of the profilers I tried failed when used with tail calls, most notably ANTS. I just end up writing my own. There is a simple implementation on CodeProject that you can use as a base.
For me SpeedTrace is the best tool on the market because it does not only help you to find bottlenecks inside your applications. It also helps you in troubleshooting scenarios to find out why your application was crashing, your setup did not install, your application hung up, your application performance is sometimes poor depending on the data input, e.g. to identify slow db transactions.
Don't forget the awesome scitech .net memory profiler
It's great for tracking down why your .net app is running out of memory.
I would add that dotTrace's ability to diff memory and performance trace sessions is absolutely invaluable (ANTS may also have a memory diff feature, but I didn't see a performance diff).
Being able to run a profiling session before and after a bug fix or enhancement, then compare the results is incredibly valuable, especially with a mammoth legacy .NET application (as in my case) where performance was never a priority and where finding bottlenecks could be VERY tedious. Doing a before-and-after diff allows you to see the change in call count for each method and the change in duration for each method.
This is helpful not only during code changes, but also if you have an application that uses a different database, say, for each client/customer. If one customer complains of slowness, you can run a profiling session using their database and compare the results with a "fast" database to determine which operations are contributing to the slowness. Of course there are many database-side performance tools, but sometimes I really helps to see the performance metrics from the application side (since that's closer to what the user's actually seeing).
Bottom line: dotTrace works great, and the diff is invaluable.
If you're on ASP.NET MVC, you can try MVCMiniProfiler (http://benjii.me/2011/07/using-the-mvc-mini-profiler-with-entity-framework/)
If Licensing is an issue you could try WINDBG for memory profiling
I've found plenty of problems in a big C# app using this.
Usually the problem occurs during startup or shutdown as plugins are being loaded, and big data structures are being created, destroyed, serialized, or deserialized. Often they are created and initialized more than once, and change handlers get added multiple times, further compounding the problem.
In cases like this, the program can be so sluggish that only 2 samples are sufficient to pinpoint the guilty method / function / property call sites.
The NuMega True Time profiler lives on in DevPartner Studio by Micro Focus. It provides line and method level detail for .NET apps requiring only PDBs, no source needed (but it helps.) It can discriminate between algorithmically heavy routines versus those with long I/O waits using our proprietary per thread kernel mode timing driver. Version 10.5 ships with new 64-process support on February 4, 2011. Shameless plug: I work on the DevPartner product line. Follow up at http://www.DevPartner.com for news of the 10.5 launch.
Disclaimer: I am the Product Manager for DevPartner at Micro Focus.
I must bring an amazing tool to your notice which i have used sometime back. AVICode Interceptor Studio. In my previous company we used this wonderful tool to profile the webapplication (This is supposed to be the single largest web application in the world and the largest civilian IT project ever done). The performance team did wonders with the help of this magnificent tool. It is a pain to configure it, but that is a one time activity and i would say it is worth the time. Checkout this page for details.
I've worked with RedGate's profiler in the past. Did the job for me.
The latest version of ANTS memory profiler (I think it's 5) simply rocks!!! I was haunting a leak using WinDbg and SOS since it proved to be the best way before, then I tried ANTS and I got it in minutes. Really a wonderful piece of software.
While not yet as full-featured as some of the other .NET memory profilers listed here, there is a new entry on the market called JustTrace. It's made by Telerik and it's primary goal is to make tracing/profiling easier and faster to do for all types of apps (web/Silverlight/desktop).
If you've ever found profiling and optimization intimidating or slow with other tools, then JustTrace might be worth a look.
If you're looking for something quick, easy, and free, http://code.google.com/p/slimtune/ seems to do the job fine.
I recently discovered EQATEC Profiler http://www.eqatec.com/tools/profiler. It works with most .NET versions and on a bunch of platforms. It is easy to use and parts of it is free, even for commercial use.
I've been working with JetBrains dotTrace for WinForms and Console Apps (not tested on ASP.net yet), and it works quite well:
They recently also added a "Personal License" that is significantly cheaper than the corporate one. Still, if anyone else knows some cheaper or even free ones, I'd like to hear as well :-)
We selected YourKit Profiler for .NET in my company as it was the best value (price vs. feature). For a small company that wants to have flexible licensing (floating licenses) it was a perfect choice - ANTS was developer seat locket at the time.
Also, it provided us with the ability to attach to the running process which was not possible with dotTrace. Beware though that attaching is not the best option as everything .NET will slow down, but this was the only way to profile .NET applications started by other processes. Feature wise, ANTS and dotTrace were better - but in the end YourKit was good enough.
I doubt that the profiler which comes with Visual Studio Team System is the best profiler, but I have found it to be good enough on many occasions. What specifically do you need beyond what VS offers?
EDIT: Unfortunately it is only available in VS Team System, but if you have access to that it is worth checking out.
I've been testing Telerik's JustTrace recently and although it is well away from a finished product the guys are going in the right direction.