The best replacement for shells is bullets.

The best alternatives to shells are rated as following:
★★★★★  bullets
★★★  energy levels
★★★  jin
★★  jae millz
★★  eyedea
★★  seashells
★★  orbitals
★★  slugs
★  manicotti
★  maple shells
★  casings
★  washers
★  3 inch shells
★  main energy level
★  orbits
★  tank tops
  glass beads
  brass
  maple drum shells
  grafh
  young zee
  jae mills
  metal shells
  low brass
  toppers
  steel shells
  3 1 2 inch shells
  remington 410 shells
  plates
  wood shells
  3.5 shells
  hd shells

Your alternative for shells is not listed? Suggest!
Speaking about shells, one probably shouldn't forget about eggs.

Other search terms related to shells and their ratings are:
★★★★★ eggs
★★★★★ place cards
★★★ cooking shells
You have in mind a companion for shells and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of shells in all years. Click on graph for more.
shells
bullets
energy levels