What other alliterative phrases have become inseparable? [closed]

• alas and alack
• bear the brunt
• born and bred
• with courage and conviction
• fit as a fiddle
• hearth and home
• kit and kaboodle
• life and limb
• now or never
• spick and span
• vim and vigor
• zig and zag

Filling in some letters joshdick missed:

• Dearly departed
• Goodness gracious (thanks for the tip)
• jump for joy
• mop and maw (a child making a face)
• pride and prejudice
• road rage

And some duplicates:

• Always avoid alliteration
• hems and haws

Just for the sake of filling out the alphabet (this answer is community wiki, so please help where I’m still coming up blank):

• each and every;
• I?
• over and out
• Q?
• time and tide, top and tail
• up and under(?)
• warp and weft (or woof); wax and wane; world wide web…
• X?
• Yin and Yang; you and yours.

Of course, alliteration is really about phonemes not letters (as the OP exemplifies with cheap and cheerful), so we should really try to collect more than just the alphabet:

• short, sharp shock
• through thick and thin
• then and there
• whys and wherefores (depending on dialect, this may or may not deserve separation from the other w’s above)
• trick or treat

A few others come to mind:

• Kith and kin
• Head over heels

The latter should evoke someone tumbling, usually in love, but most of our heads are normally above our heels. Perhaps the phrase should be "heels over head in love."