I reccently had the urge to play some of my other games that allows gamers to create mods/customizations (ima use the term very loosely). Some of the games I've played are: Halo3, Warcraft III, Little big planet, Kingdom Hearts, Sim2, Spore, Half life. Civilization IV, Guitar hero. Some games are complete mod tools for their games like Garys mod and Worldedit (warcraft III) to games that have some obscure useless customizations like Gummi ships (kingdom hearts). Some games ARE about customizing ie Simulation games like the Sims.

Besides Starcraft, what other games have you tried editing/modding/using its custom features???

Here is a list of few experiences of mine:

Halo 3 has this small map editing tool where you can place things anywhere on certain maps. I made this house that had tons of mines and jump pads and when someone goes in and kills a mine, their bodies gets launched through the chimney.

Warcraft III has one of the best editing tool. You can change anything you want from stats of all heroes to scenic looking terrain. People have created really good modded games like Dota. I am still playing through the campaign. I have also played the default custom maps. When I played the sheep map for the first time, I was easily amused by how my unit was moving using keys. I forgot that map making on war3 wasn't as limited as SC.
I don't have the skills to enjoy DotA. Just one mistake or asking a question and people get really mad. At least I can enjoy playing lots of rpg maps people make or any hero arenas.

Little big planet is a 3d graphic side scrolling game like super mario bros. Players can also create their own levels. I've tried to make a level similar to super mario but failed. Fortunately, lots of other people have done it too and i've seen couple youtube videos on it.

Kingdom hearts is an disney/final fantasy - adventure game. It allows players to customize and build their own space ship in a lego like way. I've made one thats shape like an FF airship (sort of).

My boyfriend likes his Half-life, Guitar hero and soul calibur. Half-life has this program called Gary's mod. It allows people to mod the half-life game completly. I've seen it, Its really complex, Its like the Sims for guys.
I heard Guitar hero now has a music editor where you can share and create custom songs. This is only on Guitar hero 4; we only have Guitar hero 1-3.

Mario paint was a game I enjoyed playing back in the day. It was a super nintendo game that was basically MS paint equipped with a mouse controller and pad. One of the cool things i've customized was the music sheet. I even recreated the theme from tetris using Gameboy and Star notes.

Well, that's not what I call modding really but I've tried Age of the empires 2 (and expansion) only. Did some maps and tried to make bounds for it too

Those are just like the equivalent of the SC map making program, which I don't consider modding.

Aside from that, I'm spent tons of time on Little Big Planet making useless levels that are ultimately impossible to complete. I also like making rhythm-less speed-drumming songs on Guitar Hero: WT that are also impossible to complete.

I tried making maps for WC3, but never finished any of them. I did make a couple of maps for a cool little game called "Need For Kill".

I've modded Lego star wars for PC. That was pretty easy with a simpke txt file. It was for lolz more than anything. R2D2 too big to get through the door, and Quigon this little midget that can barely get over the door lintel...heh.
I also made some custom skins for anakin i think, but they sucked.

Now i'm REALLY excited about SC2 ><"!

I have LBP too.. but its online component is Fail compared to SC (beaten by a 12 year old game...).. You can't choose who to join with.. the Rating system is very limited, It takes forever to get into a game.. and sometimes when you FINALLY join a game, the player(S) is/are already done with the game... What the F*ck?!?!? Not to mention that if people are trying to join midgame.. it lags!!!

I don't understand why there isn't a button while you selected a game that says "Wait for Players".. and you click it.. you can mess around your pod for as long as you want, and wait for other players to join.. enter your pod, DL the map, and start the game...

I bet the tools in LBP are wonderful and have unlimited possibilites.. but its online capabilities is CRAP! Which is why I haven't made a single map in it yet.. because what're the chances of yours being played? :\...

I mod Baldur's Gate frequently. Not so much mod, but change items and crap, though I did make one simple mod and packed it up in a tp2. It's nothing like Tactics or anything.

Because I modded StarCraft I modded old Gameboy Pokemon game ROMS. (Now THAT was hard. None of these sissy GUI programs. Every single you wanted to do, you had to hex edit. The basic majority of the knowledge was where the offsets are, and when I stopped doing it someone was making a BASIC map editor.)

Then shortly after than, I modded Diablo I. It was also before modding for that really picked up, but I more or less chose to keep doing things the hard way with it.

Then, StarCraft.

Then, The Sims 2, Roller Coaster Tycoon 1/2, Black & White 2, probably some other games.

Now, The Sims 3. I messed around with Lua in GMod for awhile too. I'm probably gonna wind up modding Bioshock soon, and I am going back to my roots and rewriting the Pokemon engine in a webpage. ;o

I don't MOD as such, but I've made many a custom WC3 map, and messed around with Garry's Mod a bit.

I didn't really do much modding of any sort, but for lulz I swapped out the character's voices in Baldur's Gate for starcraft sounds. The alternate terran ghost death ["TGhdth01" or something] was epic in BG II: SoA.

Heh, I used to do that in WarCraft 2. All my grunts made the Hydralisk's spawn noise, and my Footmen had the Marine sound set.

I completely forgot to mention Guitar Hero.

I've modded them all since GH3.