The cone snail (genus Conus) peptides known as conopeptides or conotoxins typically consist of about 10-50 amino acid (AA) residues. The peptides are processed from larger precursors with many more AA residues. Different regions of the peptide precursors (signal sequence, propeptide, mature peptide) have significantly diverged and are practically used as basis for the classification of Conus peptides into superfamilies. Peptides of a superfamily have highly homologous signal sequences and few variable AA residues in propeptide regions. Generally, the mature peptides (conopeptides) have relatively more variable AA residues. Peptide diversity also occurs in members of the same superfamily that differ in their molecular targets or members of different superfamilies that have the same molecular target. Conotoxins are highly selective antagonists of ligand-gated and voltage-gated ion channels. Consequently, they are used to characterize specific subtypes of receptors or ion channels. This overview describes the structural and functional diversity of conotoxins that influence neurotransmission through their action on nicotinic acetylcholine receptors (nAChRs), to demonstrate molecular diversity in various classes of Conus peptides. The primary structures, cysteine patterns, disulfide bonding frameworks, physiological effects and target specificities are described. The occurrence of these peptides in Conus venoms gives insights into the evolutionary tactics of cone snails. The conotoxins are useful as tools for investigating the structure and physiological roles of nAChRs. As the structural and functional diversity of conotoxins continues to be explored, these peptides can possibly reveal important neuropharmacological applications and therapeutic potential.