Here are my base style_formats that I use for most projects:
style_formats: [
{ title: 'Intro', block: 'div', classes: 'intro', wrapper: true, merge_siblings: false },
{ title: 'Divider Line', selector: 'p,h1,h2,h3,h4,h5,h6,div', classes: 'divider' },
{ title: 'Feature Box', block: 'div', classes: 'feature-box', wrapper: true, merge_siblings: false },
{ title: 'Inset Box', block: 'div', classes: 'inset-box', wrapper: true, merge_siblings: false },
{ title: 'Pullquote', block: 'div', classes: 'pullquote', wrapper: true, merge_siblings: false },
{ title: 'Button', selector: 'a', classes: 'btn'},
{ title: 'Images', items: [
{ title: 'Float left', block: 'div', classes: 'floatLeft', wrapper: true, merge_siblings: false },
{ title: 'Float right', block: 'div', classes: 'floatRight', wrapper: true, merge_siblings: false }
]},
{ title: 'Photo Caption', block: 'div', classes: 'photo-caption', wrapper: true, merge_siblings: false },
{ title: 'Footnote/s', block: 'div', classes: 'footnotes', wrapper: true, merge_siblings: false },
{ title: 'DEV Notes', block: 'div', classes: 'note', wrapper: true, merge_siblings: false }
],