There aren't enough public examples specifically on RPG that would let me prove how habitually I use tropes, but as far as personal writing and other websites go, my top five abused tropes are the following (the lower the number, the higher the prevalence):

[list]
[*][url=http://tvtropes.org/pmwiki/pmwiki.php/Main/DeadpanSnarker]1. Deadpan Snarker[/url]
[*][url=http://tvtropes.org/pmwiki/pmwiki.php/Main/InsufferableGenius]2. Insufferable Genius[/url]
[*][url=http://tvtropes.org/pmwiki/pmwiki.php/Main/BreakTheHaughty]3. Break the Haughty[/url] (If I use 2, 3 always shows up.)
[*][url=http://tvtropes.org/pmwiki/pmwiki.php/Main/DarkAndTroubledPast]4. Dark And Troubled Past[/url]
[*][url=http://tvtropes.org/pmwiki/pmwiki.php/Main/VitriolicBestBuds]5. Vitriolic Best Buds[/url]
[/list]