Yes, believe it or not, there is actually a molecule called Arsole... and it's a ring! It is the arsenic equivalent of pyrrole, and although it is rarely found in its pure form, it is occasionally seen as a sidegroup in the form of organic arsolyls. For more information, see the paper with probably the best title of any scientific paper I've ever come across: "Studies on the Chemistry of the Arsoles", G. Markl and H. Hauptmann, J. Organomet. Chem., 248 (1983) 269. Contrary to popular belief, however, the arsoles are not aromatic...
Furthermore, the structure where arsole is fused to a benzene ring is called 'benzarsole', and apparently when it's fused to 6 benzenes is called 'sexibenzarsole', although that molecule hasn't been synthesised yet. Another well known poisonous arsenic molecule is the simple hydride, called 'arsine', with formula AsH3.
And on a related theme, I've been told of an Aryl Selenide compound with the superb shorthand of ArSe, which is both toxic and smelly. The paper it comes from in J. Am. Chem. Soc. was published by authors from, of course, the University of Aahrus!
Also, the related molecule phosphole (which just replaces As with P) is quite amusing if you are a French speaker, since it's pronounced the same as 'fausse folle' (literally false woman), which means both a 'crazy woman' and a 'drag-queen' or 'ladyboy'.
Thanks to Neil Brookes, Nicholas Welham, Andy Shipway and Lloyd Evans for some of the info about these molecules. Another intriguing reference supplied by Patrick Wallace is: Gottfried Märkl and Hagen Hauptmann, "Unusual Substitution in an Arsole Ring", Angew. Chem. 84, (1972) 439. Thanks also to Thomas Jeanmaire for the info and translation about phosphole.