The most upvoted posts seem to be by men who were already in a relationship with a girl. So to make up for the gender imbalance, here is what I did for a guy, who I liked but he did not even know I liked him. (For the first 3 points below, he probably knew I existed but we hadn't even like said a "hi" to each other!)

Background: He was in my class when I was in college and I was truly, madly, deeply, (aka crazily) in love with him.

1. Bicycling around campus in the hot (and I mean 112F hot!) sun for hours at end hoping to "casually" run into him: I can hear someone say stalker, so let me say outright I wasn't trying to follow him everywhere per se. Just hoped to run into him somewhere so we might strike up a conversation. Might I mention that the temperatures in my college average 105F in the summer, touching upto 112F.

2. Rejecting a summer internship to stay back on campus because he was going to: I got this opportunity to work with a small firm in my 3rd year of engineering. It would have been an amazing experience, except he was going to be on campus. I just made up an excuse of working with a professor on some summer project and stayed back. For most of the summer, I did (1) above. Screwed up my project, and lost an opportunity to convert an internship into a job. Oh, and I ran into him only once during that entire summer. (See (3) below)

3. Losing my brand new cellphone because I was too lost in looking at him: At the beginning of the summer (on my birthday actually), I had bought this amazing super-sleek phone (which was very much in vogue then) that was a little more expensive than I should have spent. Towards the end of that summer, one day when I was bicycling away, I saw him walk out of the library into the shopping area (which had the restaurants and coffee shops and stuff). I entered the restaurant that he did, and thought I might maybe join him for lunch "casually". While I was still placing my order, I saw him walk out and then I realized I wasn't even hungry and didn't care about completing my order. So I walked out of the restaurant, but couldn't find him anywhere. I turned back and realized (ya, you guessed right!) my cellphone was gone. I had left it at the counter and by now somebody had flicked it. I searched, asked the restaurant people etc. but nope. Nada.
I had to make do without one for a few months before I bought another really basic phone.

4. This is the biggest of them all. Giving up grad school to work in the same city as him: By the time I was in my graduating year, we both had got job offers in the same city. I wasn't actually looking to work because I wanted to go on to grad school- the job was my backup in case I didn't get any admits. I had given my GRE and scored well and shortlisted schools. I even had an SOP draft ready. All I needed to do was sit down and fill applications. But then I heard about his job offer. I texted him to congratulate (by then we were acquaintances.) and had a general chat about whether he was going to take it up. The minute he sent a reply saying "Planning to work for 2 years and then maybe I can fund myself for grad school", I subconsciously dropped my application process. Outwardly I still tried to apply during the next few weeks, but eventually called it off and went on to take up the job.

And remember, all this when we weren't even like friends (let alone be in a relationship).

IMO, all of it was utterly completely stupid. (which is why I am posting as Anonymous). And all for love.

P.S: Once I moved to the job we actually got to talking and eventually dating. This is our fifth year in a successful relationship. Talk about romantic-movie-style story endings :) :)