* correr (to run)
* mantener (to maintain)
* hacer (to do/make)
* levantar (to lift/raise)
* caminar (to walk)
While "caminar" is *mostly* regular, its past participle ("caminaDO") is considered irregular by some linguists due to its stem change and thus is included as an irregular verb. The irregularity of the others is more pronounced in their conjugations.