Band Pass Filters for MHz
I get an extremly small value for my capacitor, even with resistors of
  low resistance. Should the capacitor then just be leaved?


Of course you don't omit the capacitor. If R is 100 ohms then C = 4pF for 400MHz. A capacitor that small is commonplace at VHF and UHF. But, for a bandpass filter I'd be looking at using inductors, capacitors and resistors to get a sharper rejection of unwanted frequencies. It all depends on exactly what you require of the filter.

This interactive calculator allows an RLC bandpass filter to be simulated like this: -





The value for the capacitor is 27 pF and the inductor is 6 nH.