Not a perfect list by any means, but it's a good start.
1. haha = I’m acknowledging that you’ve said something you perceive to be funny, though I don’t find it particularly funny myself.
2. haha. = I am weary and loathe to laugh, but here, you have forced it upon me; OR: I hate you.
3. haha! = I am pleasantly surprised to learn you are capable of modest humor.
4. ha ha ha = Very funny, you fucking asshole. You piece of shit.
5. ha = I am actually the most furious I have ever been in my entire life.
6. ha. = I knew it. I knew it. It is very tiring to be right about everything, but I live with it.
7. ha! = Clever little joke, sonny!
8. HA = Vengeance and/or justice has been served appropriately.
9. hah = Three-quarters of the way toward typing the most tepid indication of appreciation there is, I became too bored to continue.
10. haaaaaa = I am disgusted with (but not surprised by) humankind.
11. hehe = I am a middle-aged, self-proclaimed pickup artist who is pleased to have recently discovered Reddit.
12. hehehe = I just said something intended to be mildly sexual, but now I’m realizing it was maybe not clear that it was mildly sexual, so maybe I’ll quickly also type the laughter of a cartoon villain wearing an eye patch???
13. heh = I have never experienced mirth, nor do I expect to.
14. heh heh = I am cautiously optimistic about my own evil plans.
15. muahaha = I am very optimistic about my own evil plans, and possibly an actually bad person.
16. mwahaha = I am very optimistic about my own evil plans, and possibly an actually bad person, and not a great speller.
17. heehee = I have done something mildly transgressive.
18. teehee = I have done something mildly transgressive and I think it’s adorable.
19. hahaha = That was funny! I legitimately laughed, or at least smiled, and I am slightly happier now than I was before you just said that.
20. ahahaha = Like “hahaha,” but less concerned with appearances.
21. bahaha = Like “ahahaha,” but less concerned with appearances.
22. gahaha = Like “bahaha,” but less concerned with appearances.
23. hahahaha (etc.) = What you just said was really funny. OR: What you said was only kind of funny, but I want to have sex with you.
24. haha…… = Gooooooooooo fuck yourself.
25. HAHA = I made an audible laughter-type sound at this!!
26. HAHAHA = I am IRL laughing so much!!!!!
27. HAHAHAHAHAHAHA (etc.) = I am starting to panic that I may never stop laughing!!!!!!!!!!!!
28. lol = I feel nothing. I want this sentence/conversation to be over but lack the wherewithal to end it directly, with purpose; I want to admit to a feeling but lack the conviction; I want to tell you how you’ve hurt me but want more to pretend I am invincible; I want to laugh, really laugh, but do not remember how; OR, maybe: that was funny, whatever.
29. Lol (sent from iPhone) = The above, but with an added element of Autocorrect shame. I did not mean to be so formal; I wanted it clear how little I cared.
30. lol. = Like “ha.” but sadder. Angrier.
31. lolol(etc.) = I am so self-conscious right now!!! What am I sayinggggg, ever!
32. lolllllll = I feel beneath my skin surface a brimming hysteria, an existential query both exhausting and frantic: what am I doing here? The things that amuse me now are so different from anything I could have imagined as a young child. Partway through typing I realized the absurdity, the smallness of that which made me lol, and so I held my finger firm upon the “l” key for a while, and I wondered what would happen if I held it there forever.
33. LOL = I briefly, but not disingenuously, chuckled.
34. L-O-L/L.O.L. = I want nothing more than to cry. OR: I made a joke and I’m your dad.
35. lolz = I am Gchatting/texting with two to four other people at this time; each of them is significantly more interesting than you.
36. lulz = I am Gchatting/texting with five to seven other people at this time; each of them is significantly more interesting than you.
37. lmao = That is the dumbest thing I’ve ever heard.
38. lmfao = That is the dumbest fucking thing I’ve ever heard.
39. lmbo = I’m neither laughing nor happy, but I am arguing a point I’m pleased with in my role as a person who works on the internet.
40. rofl = I am an extraterrestrial who learned to approximate human language by scanning millions of pages of AOL chat logs collected in the early 2000s.
41. roflcopter = I am a police officer working the undercover teen drug-use chatroom circuit.
42. lollerskates/lollercoaster = Sometime between 2000 and 2004 I was a starred internet forum poster, and someone I chatted with regularly — someone a little older, whom I looked up to, someone with lots of x’s in his/her username — used this word, and I was overcome by impossible coolness. I am now grown, and quite serious, and typically hyper-articulate. But sometimes, when I find something a little funny, I indicate pleasure with an improbable portmanteau like this one, and I feel again that I am young, and excited, and waiting to get online.
From the hilarious cut-ups at BuzzFeed!