Total Recommendations: 3
I would more accurately recommend the various manga of Getter Robo, which should be read first to fully understand the Getter OVAs, but this is similar enough I suppose. Getter Robo is the most obvious of Gurren Lagann's many influences. The visual style of the battles in TTGL is reminiscent of Change!! Getter Robo, as well as the hot-blooded nature of the protagonists, and the similar concepts of Getter Rays and Spiral Power. Perhaps most blatantly, TTGL ripped the nature and motivations of its final villain directly from the later entries in the Getter saga, particularly Shin Getter Robo (the 1998 manga). The Getter also uses drills occasionally, if you're into that kind of thing.
Kill la Kill was basically a retread of Re: Cutie made by some of the same people. Some of the characters were new and interesting, but the artstyle, action, and humor were just watered-down RCH. Watch Re: Cutey honey if you want to see a better, shorter Kill la Kill (or if you're a fan of Imaishi, Anno, or Go Nagai).
Both feature a wanderer in a future wasteland who fights to protect the weak by making his opponents explode. Both also have very creative (if limited by budget) fight scenes, and as a bonus, the villains Braiking Boss and Raoh share a very intimidating voice actor. (Actually read Hokuto's manga, it's way better, but we can't rec manga to anime really. Casshern has no manga.)