A parasitic wasp (Hymenoepimecis argyraphaga) takes control over the spider Plesiometa argyra and forces it to wrap itself in it's silk instead of weaving a net. In the sting, larvae of the wasp develop and eat the spider from the inside while it's still alive:
The green jewel wasp (Ampulex compressa) inserts neurotoxins into cockroaches which turn them into low responsive and not attentive zombies. Again, the wasp lays eggs into the live cockroach (Periplaneta americana) and the developing larvae digest the host.
The nematode Leucochloridium paradoxum infects snakes and not only takes control of their brain by forcing them to move into exposed areas. It also moves into the snakes eyes to form pulsating protrusions which can be easily detected by birds, the final hosts of Leucochloridium.
If you think now that only insects or snails can be brain controlled by parasites, watch out: The parasitic protozoa Toxoplasma gondii (no cure for infection, about 70-80% of all mankind are already hosts) leads humans to takes risks easier and be more aggressive. Since the final host of the parasites are cats, one theory is that the parasite makes humans take more risk so they can be attacked and eaten by tigers or lions more easily...