I recently found another gem of open source engineering:
Sumatra PDF viewer
Adobe Acrobat clocks in at about 70 megabytes nowadays, plugins included. It also takes forever to start up and the update feature keeps giving you these reminders that you can't fully turn off.
Sumatra PDF takes up less than ONE megabytes and loads just about as fast as Wordpad. It has the important functions of Adobe Acrobat, but unfortunately lacks a search function. This program is still being worked on today though, the latest release being yesterday. I'm quite happy with this find.