Large RAM, Multiple Cores, NVIDIA GPUs, Basic Make Toolchain
Generally when doing development I try to place all the tiers of my webapp on my local box... it encourages me both take a devops/bootstrap mentality when doing development. On the plus side that encourages developers to know the whole stack, but on the downside it eats RAM. 8 GB of RAM is the default now on our developer workstations.
Also multiple cores within a CPU seems to count more than the actual clock speed - so four hyperthreaded cores are more valuable than four overclocked cores.
NVIDIA GPUs are also highly coveted within the development team, especially for those that run Linux. ATi's Linux drivers have always been horrible, especially with multi-montior setups. KDE4 has made configuring these and switching to projectors much easier, but NVIDIA seems to handle things better. The big test is always this: can I detach from my second monitor, walk to a conference room and connect to a projector without re-starting X?
As far as pre-installed stuff... if I have enough of a C/C++/Make toolchain going to re-build the kernel I generally can do whatever I need. I have yet to see a Linux distro actually bundle Java/Eclipse/NetBeans well, so I always prefer to download and install the latest on my own. Unfortunately OpenJDK isn't quite ready for prime time yet either... so I'm always using Sun's (yeah, I said it) JDK. If there was an easier way to install with updating /etc/alternatives that would be awesome.