Pro kennex rackets are some of the best as they were made very well and play great.
The various ace models are usually the most reasonable to find, see the below pic for some examples:
PK made some total control tight string pattern models like the micro that many collectors like to display:
This pics shows one of the models with a wood core which made for a very nice old school hit:
And the redondos are some of the best player models which hit very similar to the famous pc600s:
Most all players that played PK like PK rackets