Bruxelles-Midi - Ostende route with the HLE 13 and the HLE 13 (Double-decker) stopping at Ghent-Saint-Pierre, Bruges and terminus at Ostende. Bruxelles-Midi - Anvers Centrale route with the Thalys (no stops till Anvers) and the AM08 (S1) stopping at all stations on the route to Anvers and the HLE 13 (Double decker) stopping at some stations on the route to Anvers Bruxelles-Midi - Liége Guillemins route with the Thalys/BR406 (no stops till Liège) and the AM08 (S2) stopping at all stations till his terminus (Louvain)
Somebody suggested Aachen - Liège, which I really liked. Adding both the fast and the normal lines (including the branch to Spa), would make it a great complement (and Thalys-addition) to Aachen-Köln which everyone has, adding a scenic trip through the Ardennes and one of the most beautiful stations in the world.
