Let's See....
My favorite skill is Dungeoneering. I have always been interested in doing that sort of thing (grouping together, raiding a dungeon for resources, fighting monsters, solving puzzles, and disabling traps, etc.) in runescape, so I was really, really excited when they first released it. I am also a really big lore person, always trying to find out the meaning behind what happens in the game, and I do particularly love the lore behind Deamonheim. I also love a lot of the bosses, especially the Demons-my favorite is Yk'Lagor. I was obsessed with fighting him when he first came out, and I still remember actually doing so for the first time as one of my favorite first encounters with "new" content.
Basically I love just about everything about Dungeoneering, which means the skill is never a grind for me ;D
Quests..well I have a couple of favorites.
I loved and was absolutely amazed by "One Piercing Note" when it came out. I thought it was a terrifically done quest, the voice acting and music really helped create a fantastic atmosphere, and the quest even had an emotional side as well-and helped show that not everything is purely black and white.
Despite possibly being quite frustrated while actually in the process of doing them, I do awfully enjoy quests with really hard puzzles. Mostly because I like being forced to use my mind to solve something in runescape, not merely bash things over the head and overwhelm them with my high skill levels. I like something where I can feel its me, not just the couple of pixels representing me, doing the work. Therefore, I did particularly like doing quests like "Elemental Workshop III" and "Mourning Ends II-Temple of Light."
Another quest I loved was "Branches of Darkmeyer." I mean, I love the entire Meryque story-line in general, but this quest was definitly the best in the lot. Everything about it, from music to graphics to content, I thought was great. The boss fight was fun as well, even though I think it holds my current record for "most deaths on a quest boss ever."And of course, the rewards from the quest were amazing to
Finally, I (along with 75% of the rs community) realy enjoyed "While Guthix Sleeps" For me, this is mostly because I felt it had just about everything in it that a quest needs. It had exploration of new areas; fighting (including a tough, high level boss fight at the end); a great story line with both emotional and lasting impacts on the story of game itself (as in, other game characters knew it happened, and things you did in game changed because of it); and "overboss" that, at least at the time, was simply to tough for you to deal with and presented a constant looming threat.
It also had great rewards- lots of experience to reward you for the time spent on the quest, a high priced (for quests at least) instant monetary reward, and access to a new area to fight new monsters to get money and new, better equipment.
Finally, it had something I find lacking in many of the more recent quests. Nowadays, it seems that every new quest has a specific, small area it takes place in, and you always have it quite easy finding out where to go and what to do. In While Guthix Sleeps, you are released and have to trek over the entire world over the course of the quest, which is something I rather miss doing.
Monsters I enjoy fighting...
Well, I enjoy monsters that take more then "click attack, thenstand there and wait till they die." So my favorite monster to fight that I have actually beaten and fought many times would have to be Tormented Demons. I actually have a thread somewhere (
rsjedi.proboards.com/index.cgi?board=runechat&action=display&thread=8380) on why I enjoy them, but I'll summarize here. I like fighting them because they require both offensive and defensive strategy (due to protection prayers and accurate, hard hitting attacks), because they have a "special weakness," in that they require a specific weapon/item/thing to help fight them, or they are impossible/incredibly tough to defeat. I also love the music track that plays in there area, it's one of my favorites. Finally, I like that they have good drops, worth a lot of money, that are , while still rare, easier to get then a GWD drop or Corp Drop.
Even tough I have never been able to actually kill these (solo and in the current game,not using Deathtouched darts, that is) my next two favorite monsters would be Nex and the Queen Black Dragon, both for much the same reasons as Tormented Demons. They both require strategy to fight-if you don't pay attention to their attacks and what they are doing, you can easily die.
Furthermore, I do like the idea of there being Massive/powerful creatures around that you simply cannot defeat, no matter how hard you try. I have never understood why/how our character could defeat things 2,4,6 times his level on his own, so I actually like that Nex is unsoloable.
Even the QBD- she has to be fought solo, but then, she provides you with one of the the hardest fights in your rs career, and yet you fight her in a weakened, half awake state, in the end only managing to put her back to sleep.
As for my favorite activity/minigame...
Well, I like Barrows, but that's mostly because I like using Magic, and it is beneficial to do so there, unlike so many other places on rs.
I also had a lot of fun with Temple Trekking after it's rework, though now, with only the two hardest companions to level up just a few, long levels, I mostly get annoyed at that idiot old man who thinks he's a badass and runs around attacking everything and getting killed.
While I'm not quite as into it now as I once was ( though I still do enjoy it a lot), when it first came out I was absolutely obsessed with Stealing Creation. I played it nearly every minute of free time I had, including some not so free time. I think my craze with it calmed down about a month after it came out, but till then I couldn't get enough of it.
As for other games, I like Soul Wars and Castle Wars both for the social aspect, and for the fact that they give me a place to really benefit from my single 99
Pest Control is where I go on those rare occasions that I
do feel simply ion the mood of bashing things over the head.
Finally, most minigames and activities I play now have significantly increased enjoyment added to them if I can do them with friends and clan.
Both require a bit more attention than most skills and are a bit inconsistent at times, which makes them fun 
My absolute least favorite quest was Underground Pass. Dat do-do was gay.
