MB DIY diagnostic tools recommendations??

[ichbdkevin]

All:

Was wondering what tools you'd recommend (and their online ordering sources) for a shadetree mechanic to keep in their box to work on a 190e 2.6...???

Here is what I'm thinking...any other additions would be helpful:
Fuel pressure tester
Fuel injection tester
DMM with Duty Cycle

What else?

Cheap $$$ sources for Mercedes specific diagnostics would be a big help.

Thanks.