For some reason, Whenever I am sitting down and my cat comes near me, she starts smelling my pants. She rubs her chin on them and starts acting all playful. Is this for attention, or is she trying to mark her territory? I have heard that cats rub against you to mark you with scent glands under the chin, but do they usually get so playful during this? It isn't bad or anything (actually, it kind of tickles), but I was just wondering.

If she is a female and not desexed she could just be horny lol girls do a lot of strange things when on heat. Otherwise she is probably marking her territory and being affectionate at the same time, or is just in a playful mood.