Using all letters

                                                                           speechlessly

                                                                          The other words:

                                                                               cheep

                                                                              cheeps

                                                                               clepe

                                                                               epees

                                                                             helpless

                                                                            helplessly

                                                                               helps

                                                                               hypes

                                                                               peels

                                                                               peeps

                                                                               peppy

                                                                               psych

                                                                              psyche

                                                                              psyches

                                                                              psychs

                                                                              schlep

                                                                              schlepp

                                                                             schlepps

                                                                              schleps

                                                                               seeps

                                                                               seepy

                                                                               sheep

                                                                               shlep

                                                                               sleep

                                                                             sleepless

                                                                              sleeps

                                                                              sleepy

                                                                               specs

                                                                              speech

                                                                             speeches

                                                                            speechless

                                                                               spell

                                                                              spells

                                                                               sylph

                                                                              sylphs

                                                                              sylphy

                                                                               yelps