Blistex

Things you'll need to be effective.

A barebones PIII, P4, AMD, AMD XP systems (troubleshooting units)
A CD-RW (for backing up people's crap)
A few HD's (for extra fast installation of common software)
A few hardware 56k modems (people always need them)
A few 10/100 Nic's (people love to network their PC's)

If you're really strung for cash you can change over all the hardware between the 4 barebones systems so as to not have to buy 4 videocards, HD's, and the rest of the stuff.

And a Win 95, 98, 98 SE, ME, NT, 2k, XP Home, XP Pro for those people who leave their CD's at home when you need them for hardware and software installations.