What are some good web based trouble ticket systems?

I'm looking for a trouble ticket system so that I can track issues for various customers. I used one before at my previous employer but it wasn't anything too great. I'm wondering which ones you would recommend and what other features that I might want to look at to make my job easier. It must posses the following.

1. Web based
2. Handle multiple clients (probably all support this)
3. Asset management

Commercial Products:

• Atlassian Jira (which ties in nicely with Confluence (the wiki)) - Surprisingly good for commercial software.

Open Source:

• Edgewall Trac - (Wiki, Ticketing, and more)
• Drupal (+plugin)
• Best Practical RT - I've heard good things about this, but have never used it myself

I would suggest Request Tracker (RT) with the AssetTracker plugin.

RT: http://bestpractical.com/rt/

Plugin: http://wiki.bestpractical.com/view/AssetTracker

We use FogBugz for bug tracking, but it's expensive ($100 per developer) and depending on how you feel, the interface is so-so.

We also use Trac for internal help desk ticketing; depending on how you feel, the interface is worse, but it's much cheaper. You have to run your own server with Python though.

And you can also use 37Signals's HighRise, which I've heard some people have had some success turning into a helpdesk system. It'll keep track of all your correspondence and attachments. But using it will involve tweaking your notions of a help ticket system, which in some ways is a good thing.