Most Linux, BSD, MacOS machines come with /usr/share/dict/words so a little awk, grep, and other shell utilities can find some interesting words.

The longest words consisting of only vowels

user$ awk '
  !/^[aeiou]*$/ {next}
  length == m {a[++i]=$0}
  length > m {delete a; a[i=0]=$0; m=length}
  END {for (i in a) print a[i]}
  ' /usr/share/dict/words

The longest words you can type with the left hand

user$ awk '
  !/^[qwertasdfgzxcvb]*$/ {next}
  length == m {a[++i]=$0}
  length > m {delete a; a[i=0]=$0; m=length}
  END {for (i in a) print a[i]}
  ' /usr/share/dict/words

The longest words you can type with the right hand

user$ awk '
  !/^[yuiophjklnm]*$/ {next}
  length == m {a[++i]=$0}
  length > m {delete a; a[i=0]=$0; m=length}
  END {for (i in a) print a[i]}
  ' /usr/share/dict/words

Words you can make out of SNICKERS singles

Around Halloween, the kids often get these Snickers singles with one letter per disappointing chocolate. What words can we spell with them?

user$ grep '^[snickers]*$' /usr/share/dict/words

The longest words you can type alternating hands

user$ awk '
  !(/^[qwertasdfgzxcvb]([yuiophjklnm][qwertasdfgzxcvb])*$/ || /^[yuiophjklnm]([qwertasdfgzxcvb][yuiophjklnm])*$/) {next}
  length == m {a[++i]=$0}
  length > m {delete a; a[i=0]=$0; m=length}
  END {for (i in a) print a[i]}
  ' /usr/share/dict/words

Words containing the same letter 3 times consecutively

user$ grep '\(.\)\1\1' /usr/share/dict/words