Aside from being a human, which is a very relevant creature type in Commander, Modern and basically every other MTG format, Esper Sentinel is good because it reads: Whenever an opponent casts their first noncreature spell each turn, draw a card unless that player pays X, where X is Esper Sentinels power. Its a bit like Rhystic Study, but the cost can be far higher if youve got things that make humans stronger or you can put +1/+1 counters onto Esper Sentinel
You can only use this effect of "Prank-Kids Battle Butler" once per turn
Cards like Overlord of the Hauntwoods and Aftermath Analyst should help you get to that prerequisite in no time
However, it has massive impact on a few matchups
In the right deck, Ramos snowballs into both a gigantic flying attacker and a mana engine that fuels backbreaking turns
Number 71 Language English Legal Formats Commander, Legacy, Modern, Vintage Not Legal Formats Alchemy, Brawl, Competitive Brawl, Historic, Pauper, Pioneer, Standard, Timeless Rulings (6/1/2011) Other players, including the card's owner, can't look at the card while it remains exiled