The invisible slide bug is definitely one of the strangest.

Anyway, I love the sci-fi table and chairs from Nexus, but the table has weird layering mechanics. The chairs can be stacked, but attempting to stack the tables (or put anything on top of the table, for that matter) doesn't work correctly. The upper-half of the table always remains on the highest layer.

Also, the floating sci-if table cannot be pushed/pulled.