If you don't want to use Akismet or have problems with it, you can make use of the Spam Words text box under Settings > Discussion > Comment Moderation. You should put words there that you commonly found on spam comments.
There is also a Comment Blacklist text box under the same page where comments containing words or part of a word in the list will automatically be trashed. A list of spam words is available here codex.wordpress.org/Spam_Words. You won't need to do this if you already have Akismet installed.
If you want other plugins that will help combat spam then you should look at some CAPTCHA plugins. Popular ones are SI CAPTCHA and ReCaptcha which will ask users to enter a captcha form every time they make a comment or register.