Seeing that people here are making recommendations I might as well add a few from my collection:
1.
GaoGaiGar: If you likes Gurren Lagann and desperately need another fix of giant robo action then this is worth a go. It's available in two boxsets, both at very decent prices. The first box, the green "Bullet X Box" is SUB/DUB while the second yellow "Za Powa Box". The first twenty or so episodes are your basic monster of the week stuff mainly used to introduce the main characters and attacks, the real meat is in the remainder. Basically if you can stomach
this for nearly every episode then you will like GaoGaiGar and then will curse the anime industry until GGG Final gets licenced.
2.
Gunbuster & Gunbuster 2 Don't bother with the movie editions. If you can find them get the original OAV versions. GB comes as a single 3 disc set while GB2 is available as 3 separate single disc releases. More giant robot action from the creators of Evangelion and Gurren Lagann.
3.
Godannar: More giant robot action (seeing a pattern here?) of the combining variety from the same creative mind as GaoGaiGar with almost the same amount of recycled combination sequences but with the addition of a healthy dose of fanservice.
4.
Giant Robo: The Animation: This should be in everybody's collection.
5.
The Big O: Another giant robot show (this is getting silly now). Possibly holds the prize for
best opening sequence ever. If I had infinite money I would go over to Sunrise inc. in Japan, hand them a cheque with a lot of zeroes on it and a message saying "Make Big O season 3 now please".
6. The original
Macross is always worth looking at, along with
Macross Plus.
7.
Dai-Guard: Is what you would get if you had a Giant Robot built by the lowest bidder and then run on a shoestring budget, can't even afford a proper
Rocket Punch...
and finally
8.
Rahxephon: If you enjoyed Evangelion or
proper giant robot action isn't your thing then you can do a lot worse than this.
