Using appropriate fonts for your report
Generally a report should be word-processed and you should use a font that looks about the same size as Times New Roman 12 pt. Different fonts look slightly larger or smaller when they are supposed to be the same point size.
Serif v sans-serif
Most typefaces (i.e. fonts) fall into one of three families; serif, sans-serif and dingbats.
Serif fonts
Serif fonts are typefaces that feature 'serifs'. These are decorations on each letter. Serif fonts are often used on official documents (in the legal profession for example). Unfortunately the serifs reduce the amount of white-space between letters sometimes making the text harder to read. Well known serif fonts include Times New Roman and Courier.
Sans-serif fonts
Sans-serif fonts are typefaces without serifs ("sans" is French for "without"). Well known sans-serif fonts are Arial, Helvetica, Tahoma and Verdana.
'Ding' fonts
Dingbats are not really relevent in report writing as they are fonts made up of pictures (such as Wingdings on Windows computers).
Aim for clarity and readability
Unless otherwise instructed by your tutor (or employer) avoid using serif fonts such as Times New Roman. Use a font that's easier to read such as Arial, Tahoma or Verdana.
The three examples above enable you to compare the same text set in three different typefaces (Times New Roman, Arial and Verdana). All three examples use the same identical 12pt text. The only thing that is different is the typeface.
Don't forget - if your manager or tutor finds it easier to read your work, they're more likely to find that amazing paragraph that you spent two hours writing and re-writing! 
Stick to the policy
Needless to say, check what the policy of your employer, college or university is just in case they happen to like Times New Roman! :)
Many businesses will have a corporate policy on what fonts to use in their documents. This is sometimes known as a "house-style" and can even be part of the company's quality procedures.
If you work for a company that tells you to use a certain font for your documents then it doesn't matter how much you don't like that font, you need to stick to it! 