1) Vox hands down. Ask everyone in my office (who is like 10 years older than me too) and they say the same. Just remember to drink it Ice cold, it's like water going down with hardly any burn at all... Please don't ruin this expensive stuff by mixing it unless it's for the ladies (Cosmos).
2)Ultimat. At $53 a bottle, this stuff isn't as smooth as Vox but it's dam close! It also comes in a chic royal blue bottle (probably the most expensive I've tried).
3)Grey Goose/L'Orange. Makes a silky smooth Cosmo, especially the Orange.
4)Stoli/Orange. Also makes a killer Cosmo for the ladies.
Those are my top 3 - on the list to try are Belvedere (which I'll be cracking tonight, have an unopened bottle sitting in my room), Brilliant, Iceberg, Ketel One, Three Olives, and Tanqueray.
Ones I've tried that taste like ass: Fris, Svedka, Rain, and cheapass Gordon's (comes in plastic jugs).
Decent vodka's, but not ones I prefer to drink ever again if I can afford to: Skyy and Absolut.