Charles Van der Stappen (1843-1910), famous Belgian sculptor, is the author of this Young man with sword (Museum of Fine Arts, Brussels). He also achieved his version of David, below.
Roger Vene sculpted this 'Thinker' located in the Ixelles cemetery, near the main entrance.
In the same cemetery, another male sculpture, from Eugène de Bremaecker (1879-1963).
In the Palais des Nations, where the 'Parlement Fédéral' is located, there is a sculpture I like, discreetly visible between two corridors, made by Paul Du Bois (the Belgian sculptor, as there is a French one with similar name), and representing the young Prince Leopold.
Royal Institute for Cultural Heritage
Sculpture Publique en Belgique This website is a fantastic work compiling almost all public sculptures in Belgium, by artist or by location.