Wyse PocketCloud Remote Desktop & RDP Client - $15
This remote desktop app does everything. Right-click, gesture scrolling on the remote machine, CTRL, ALT, FN keys, drag and drop. Its worth the $15 of you are a profession, just for the RDP features. It gives you a "virtual mouse" that you can use to click, right click, scroll, etc from. Its hard to explain, but its very useful.
It also give you flash on the iPad. If you install the Thin-Browser on your remote PC, it allows you to run IE from the remote machine with your iPad's GUI as if it were an app on your iPad. This allows Flash, ActiveX, Silverlight, Java, etc. The main limit I have see is that it does not perform well with video. It works, but the video is not a smooth playback.
I have no connection to the developer, a coworker just installed it and showed it to me and I am really impressed!