High res display, excellent keyboard, good RAM
Top items on my list:
1) I find it useful to have a good 15 or 17 inch high res display - something like 1920x1200 will be amazing instead of the typical 16:9 widescreen displays. Also, 13 inch will definitely be too small for the type of work I do (J2EE development using Eclipse etc) - a minimum of a 15" display will be needed. Matte screens are better.
2) Ability to either dual boot Windows 7 or to have a virtual machine with Windows 7 pre-installed. The Windows 7 license can be sold separately. If possible, multiple such OS licenses can be sold with the same laptop - example: Windows XP and Windows 7 (for testing with IE6/7/8/9).
3) 6 GB RAM or greater. 8/16GB expansion possibilities.
4) Excellent keyboard - I can often do 1000s of lines of coding each day and so this is critical. Dedicated numeric keys will be good to have but not essential. No funky arrangement of Del, Backspace, Shift keys. Also, excellent trackpad is essential.
5) Network (RJ45) port is essential.
6) VGA port. Essential to give demos at client locations
7) Excellent battery life
8) Good speakers so that we can do video conferencing without needing to wear headphones. Also, excellent microphone with good echo cancellation.
9) IMPORTANT: Separate ports for headphone and microphones. The current crop of headphone+mic combo ports which come even with the E65xx series latitudes are a pain to work with. If we need to do even things like recording audio, it is really complicated to use these combo ports.
10) Good webcam
11) Sober colours and elegant designs like the older Precision laptops and the older Latitude D series laptops. Cannot be sitting at client offices looking like a boy gamer. Lightweight machined chassis if possible.
12) Atleast 256 GB SSD. If possible, the harddisk (SSD) to be partitioned such that a volume can optionally be encrypted.
13) DVD drive
A proper VPN client
Oracle JDK or option to download and install easily