In no particular order

Basquash: Loved the story and presentation for the most part, the robot design took some getting use to at first but eventually grew on me.
Metal Gear Solid: Rex was my favourite of the Metal Gears, the story was also great.
Code Geass: While I liked the story the robots werent really anything special.
Gurren Lagan: The robot design took some getting use to and I didnt really like the story except for the season climaxes.
Voices of a Distant Star: was an enjoyable movie and the only other mecha thing I can remember having seen at the moment.

If i cant use games then Pacific Rim was pretty cool too.

Honorable mentions:
Mechwarrior 2 had some great mech designs but I couldnt tell you the story if my life depended on it.
Neon Genesis Evangelion had a great story (particularly the manga and films) but I didnt put it on my list because (SPOILER)theyre technically not "robots" since eva's are made of people