What games have you gotten 100% of the items? What games have you gotten all endings for?

Why do you 100%? What are the most rewarding games you've 100%'d?

For myself, completionism is a pain -- I don't think I even caught all 151 Pokemon in Yellow despite putting in 100+ hours into it.

Super Mario World tells you right on the start screen how many exits you've found.  That was a strong incentive for me to find them all.

I think the only games I 100% was Chrono Trigger and  Lunar Silver Star Story (for the playstation).

It's hard to say when you've "100%'d" a game, because how do you know you REALLY got everything there is to get?

I'm lazy so I just use Trophies as a measuring stick. Do I have 100% of the Trophies? Then I 100%'d the game.

https://psnprofiles.com/Amazingu?completion=complete

If the game doesn't have Trophies, or doesn't have an in-game percentage counter of some sort, I usually don't even bother.

I always get 100% of the secrets in Tomb Raider when I play it (and also implement a no-Medipak rule to make it more challenging - which only adds any real challenge in the final level were you have to damage yourself for about 80% of your health bar in a fall to continue) but you technically can't get 100% secrets because when you pick up the last secret there's an over site in the code that doesn't allow it to register. So you can get 100% but the end ally will never read 100% unless you use another exploit to make the last secret count twice.

Final Fantasy VI
Final Fantasy VII
Final Fantasy VIII
Final Fantasy IX
Final Fantasy Tactics
Fallout
Fallout 2
Fallout 3
Fallout: New Vegas
Mass Effect
Mass Effect 2
Mass Effect 3
Assassin's Creed
Assassin's Creed 2
Persona 3
Zelda: Ocarina of Time
Zelda: Wind Waker
Zelda: Twilight Princess
Chrono Trigger
Dark Souls
Dark Souls 2
LA Noire

Many, many more.

Most proud of Mass Effect 1 and Persona 3. ME1 because I absolutely love it to death, and Persona 3 because it's hard as balls to 100%.

I try to go for 100% runs on every game I play, because it makes me feel like I got my money's worth.

Not as proud of Fallout 3 and NV. Great games, but I felt exhausted and completely burned out on Bethesda games after. Never had any desire to play 4.

Still feel Assassin's Creed 1 is the best in the series.

EDIT: Since Gen 5 (Black/White), I have completed the Pokedex in every single Pokemon game. Also really proud of that.