TalkZapp lets you send audio messages by writing them and converting them to voice.
Just click on the paperclip in Whatsapp and start writing funny messages!
There is also a full version without ads available.
-Converts text to voice and sends via Whatsapp
-Lots of languages (internet connection required for some)
-Also works with other apps like Skype and Gmail
Instructions can be found in the screenshots.
NOTE: Your phone must have a Text-to-Speech engine for Talk Zapp to work. If you don't have one you can download one from Google Play. Depending on the TTS engine, some languages that appear in the app may not work.