Most of the enchanted weapons that I give my party comes from NPC opponents. So if their opponent uses an enchanted spiked chain, then the party finds an enchanted spiked chain. I make NPCs, at least high-level NPCs, to be interesting, effective, and varied, so they have run across a number of exotic weapons, as well as more "mundane" weapons.
I also tend to associate exotic equipment with specific cultures. In my homebrew world, there is an Arabian culture where duoms are more common than elsewhere, and there is a city ruled by necromancers and spiked chain-wielding werewolves. Dwarven war axes are more common among dwarves (duh), and dire flails are more common among some mountain barbarian tribes. By keeping the opponents' equipment consistent with their background, it seems to make exotic weapons sufficiently exotic while still giving the PCs the opportunity to find some exotic equipment.