Ianto/Owen - Owen uses the spray to seduce Ianto. Ianto resists saying something like "not like this", and Owen can't bring himself to take advantage of Ianto.
Past Jack/Ianto - When Jack comes back, Ianto refuses to accept him back. Believing Jack had left because they were through, he's moved on.
Owen/Ianto - PreTorchwood, Ianto goes to a doctor for his pre-Uni physical. Owen likes his figure, and says so.
Torchwood/Doctor Who:
(9/10)Doctor/Ianto - While working in London, before he joined Torchwood, Ianto saves the Doctor's life. A grateful Doctor tries to woo Ianto in to being his companion.
Ianto/Jack - When Torchwood 1 Ianto goes to investigate a temporal disturbance in London's Eastend, Conman Captain Jack kidnaps him.