I find it funny when I hear things like "eat lesser" or "this is lesser than that" because LESS is itself a comparative adverb. It behaves the same way as MORE. So you say "more than", "less than" but you don't say "lesser than". LESSER is used in instances such as "the lesser of two evils" or "a lesser-known writer".
another common word people (I mean Singaporeans) often get wrong is REGARDLESS. they use IRREGARDLESS when they mean REGARDLESS. the suffix -LESS already negates REGARD so you do not need to add a prefix IR- and negate it again (negative negative becomes positive?? LOL). you can say IRRESPECTIVE though.
there's also INSPITE OF or DESPITE but no DESPITE OF. and COMPRISES or CONSISTS OF but no COMPRISES OF.
finally, it's WITH REGARD TO... e.g. May I talk to the supervisor WITH REGARD TO my application? REGARDS are good wishes you send to people e.g. when they're sick or you have not seen them for a long time, you say "send my regards to him."