There are nearly 400 words that match, here are a selection:
Four letter words with the same first and last letter are:areaariaaquaaurabarbblabblobbulbchicdeaddeeddieddyedeaseeaveedgeelsefiefganggonggroghashhighhushkickkooklolllullmaimneonnoonnounoleoontoOreoorzoouzopeeppimpploppomppoopprepproppulppumprearroarsanssasssoustacttartteattauttenttesttextthattilttintToottorttouttrottufttwitwhew
Ache, achy, ashy, echo, john and oohs are 4 letter words. The 3rd letter is H.
shut shun crud spud drug glut
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 4 words with the pattern --A--W. That is, six letter words with 3rd letter A and 6th letter W. In alphabetical order, they are: leasow meadow reavow shadow
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 4 words with the pattern --RAE-. That is, six letter words with 3rd letter R and 4th letter A and 5th letter E. In alphabetical order, they are: maraes peraea scraes straes