The review on applications of 2-trichloromethylbenzimidazole (TCMB) in analytical chemistry is presented. It was unexpectedly found, the uncolored TCMB reacted vigorously with pyridine at RT affording high-colored products. In reactions with some other nitrogen containing heteroaromatics (including pesticides) such as azines, azoles or benzazoles, formation of similar products occurred as well. The reaction was regioselective, since the both α-positions adjacent versus the nitrogen atom(s) must not be substituted, and sensitive. However, the attempts to develop dosimeters for nicotine failed. In a pre-chromatographic reaction of aromatic o-diamine with methyl trichloroacetimidate, TCMB derivatives were formed in situ. Followed by TLC and visualization in pyridine vapors, it was applied for detection of o-phenylenediamines. The amaranth reaction product of TCMB and pyridine (LI Complex) was isolated and identified. Two different reaction mechanisms for azines an azoles were proposed. In water, LI Complex may be used as an indicator in the analysis of inorganic salts and in acid-base titration. The work is targeted on researchers and students in organic or analytical chemistry.