Although the main toys that I play with are plastic building blocks (Lego®, Megabloks, and BestLock), I also have 3 Meccano sets, 1 Temsi set, 2 Construx sets and 5 large K'Nex sets.
A different kind of relaxation is that of assembling jigsaw puzzles. I mostly do the Wrebbit Puzz3D puzzles.
And, if I don't want to relax, there is always my Playstation 2!