The answer is that it depends what you are trying to do.
Basic results like molecular weight, pI, amino acid composition may be of use if you are trying to find the protein in a 2D gel.
if you are trying to see how the gene evolved by comparing it to other similar genes, BLAST is a good place to get started. Then use some or all of the evolutionary software tools out there. Among my favorites are BEAST and MEGA but you miliage may vary.
If you are trying to make images suitable for publication there are lots of programmes to help you.
If you protein is of unknown function EXPASY may be of use.
If the protein is an enzyme and you want to fit it into the matabolic pathways some of the references above may be of use.
if you have a set of genes rather than a single one then there are a number of programmes that will calculate the effective number of codons, the codon chi square, and allow you to do correspondance analysis to look for similarities.
If you are doing a gene by gene comparison between two genome Artiminis may be of use. There are other programmes for this task.
A little more information might be of use if you have something specific in mind