I am pretty sure I am a piker among you (youse) guys as I own only 21 engines.
My favorite road is Texas and Pacific and I have 6 T&P engines and one MP GP-20. So that's 1/3 of my roster.
My most esoteric engine is my Erie Triplex RK Imperial.
My favorite engine is my Lionel 736 Berk I decaled as SP when I was in 8th grade.
My worst engine is my dead Lionel F-3 smoking powered B unit. It ran one Christmas season and was dead the next year. Inquiries to Lionel promised a very large repair bill... still dead.