Of all the villains who befuddled the Dynamic Duo on the 1960's Batman series, Frank Gorshin's Riddler was easily the most memorable -- for his giggly, frenetic energy, for his rather clever riddles, and for his obvious crush on Robin. He preferred capturing Robin alone, with no Batman interfering, so he could caress the Boy Wonder's chest and shoulders, touch his hand, draw his face close, and look for all the world as if he wanted to kiss rather than kill him.
And for his physique. Most Batman villains were dumpy at best, but the Riddler was hot, lean and toned, and his green jumpsuit was even more revealing than Robin's (after a few episodes, the censors forced him to wear a silly green business suit to hide his obvious gifts beneath the belt).
But Frank Gorshin was more than revealing tights and frenetic energy. He began his career playing juvenile delinquents in the 1950s, and starred in dozens of movies, playing mostly villains and tough guys. A skilled impressionist, he won a Tony for playing comedy legend George Burns in the one-man show Say Goodnight, Gracie. And, although he was married for 50 years, he was reputedly gay in real life. He died in 2005.