-Pandora is great. I have Tune in Radio Pro, and it's good, but it constantly streams, so it uses more bandwidth, and for some reason, it just pauses music playback.
-Fancy Widgets Pro is a great clock/weather widget. A very simple but classy look, and has all kinds of skins. I do like weatherbug, because it puts the temp in the notification bar as well.
-Skype with video - great if you have htc lte, very sharp and clear video.
-Elixir - a great set of widgets and you can pick and choose which widgets you want in the set. i particularly like the screen off widget, since i don't have to press the power button to turn off the screen.
-setcpu - can set max and min cpu speeds as well as governor. requires root.
k9 - very fast mail app, way faster than my stock mail HTC app. allows gestures
-dolphin browser - not quite the fastest for me, but the most stable, and allows gestures as well.
-ASTRO - great file browser and can back up apps (but not data)
-Titanium Backup - back up apps+data. requires root.
-Battery monitor widget - monitors and logs your power consumption. useful to see if something in your phone is draining power.
-Data counter widget - see data stats by day, week, month. particularly useful for people on plans with limits.
Juice Defender - allows you to shut off data while the screen is off. Useful if you are in a weak signal area and searching for mobile data, or if you have apps using data when it shouldn't be. If your system doesn't have problems, and you are not in a weak signal area, then this app won't help much.
Yahoo messenger - I use it mostly just for free international texts
Google voice - i use this for domestic texts, saves me from buying a text plan.
multicon - allows you to squeeze icons into a smaller space, i use the 2x2, meaning 4 icons in the space of 1 regular icon.
Pulse - great news reader with a great widget as well.
Swiftkey - very very good text prediction. good keyboard.
flex t9 - best keyboard layout, easy to use, but kinda lousy text prediction.
volume locker - locks volume from accidental presses.
wireless tether - free wifi tether, no limits (most free tether apps do not allow secure websites). requires root
What i didn't like:
-xscope browser - constantly crashed
maildroid - slow