Silver stain

Various bacteria (e.g., Pseudomonas, Leptospira, Bartonella, Legionella, H. pylori, Treponema)
Various fungi (e.g., Aspergillus, Pneumocystis, Coccidioides, Cryptococcus, Candida)

Mnemonic

Helicobacter pylori, Legionella, Bartonella henselae, and fungi (eg, Coccidioides, Pneumocystis jirovecii, Aspergillus fumigatus)
HeLiCoPters Are silver