Brace Large, Platform XL, Platform XXL, Brace Tunnel, and Block 2x4/2x3.
Coliseum walls and the majority of building blocks are FUGLY, unfortunately. They all either cause lag, have a downright creepy obsession with z-fighting, or simply don’t work with any piece besides themselves. They have a great shape, but just cannot be used if you want a map that looks as good as it plays.
Brace larges, although they can move, look beautiful as floors, ceilings, and walls. The textured strip-style that they apply when use en-masse is as pretty as a newborn lamb, and fits with any aesthetic theme. Plus they are bright when put into the darkest depths of the hanger, and toned down when shoved beyond the boundries into the glaring sunlight, so look well no matter the location. Combine that with they ease of use, and you walk out happy.
Platform XL’s, although serving no gameplay purpose, look absolutely stunning when filling up dead space imo. They don’t do much else, but its enough to keep me happy.
Although you have to be creative when using Platform XXL’s, the bottom can be use to create a unique grid-like formation for a floor. Despite what people say about it being over-used, its the most unique piece when used correctly. And throw in an extra piece, you can have some very juicy walls using the oft-ignored sides of the XXL Platform.
Brace tunnels are my favorite aesthetic piece. Period.
Block 2x3 and 2x4 are my replacement for the much-loved Block Double back in the fabled days of Halo: 3. Used for almost everything, this block was the floors, walls, ceilings, ramps, aesthetic piece, and even janitor of the original forge. They look great, merge together easily, flow great with natural geometry, and work with anything else you can imagine (except coliseum walls, those fail.) Because of this I struggle to think of a situation that you cannot use them in; as long as they fit the aesthetic theme, you have yourself a great piece.