I'm with Bretty, I love me some beautiful women, but they won't lead me to buy the product they are surrounding.
There was pretty heated debate somewhere involving booth babes and Soda Pop Miniatures at one of the cons (it might have been on the Kickstarter comments for Relic Knights). There they have cosplayers dressed up as some of the main female characters in their miniatures game to "help promote" it. But considering it's all based on anime conventions a lot of people were put off by the amount of skin showing.
Personally I thought it was a cool idea for them to get people acting like characters in there game, rather than just some hot chicks in bathing suits. But I can see the point the folks were making.
anyway. Back on topic:
I also enjoy when achievements award me for something diffcult and it's an awesome feeling to pop an achievement on a game like Deathsmiles, Muchi Muchi Pork or another bullet hell shmup. Hell, the amount of work that went into finding every single flag in Assassin's Creed made those achievements feel worth while (also helps that I love that game).
Also @Foxhack's
What if it's a multiplayer-only game, like Team Fortress 2?
I've played the game for years and I'm not even close to getting some of these.
Online-Only games seem different to me, than a game that has a multiplayer component. Some Single Player games don't really need a online mode, and tacking one on and then making you play it if you want to get all the achievements in the game is a joke.
Now a game like TF2. I highly doubt I'll ever be anywhere close to getting all the achievements in that game. Mainly because I won't play a class I don't enjoy playing. Which is why I generally stick to Pyro, Engineer and Sniper.