I have two to confess. Since I’m totally torqued about the return of the final season of BSG, that’s where I’m going.
Crewman (and later Lt. ?) Seelix and (Gunnery?) Sgt. Mathias.
I regret that I don’t post links to images, because they are, after all, obscure, and the ones that I can find aren’t so good.
Not sure how obscure or geeky this is, but Kimmy Gibbler from Full House. I really didn’t like the show, but her quirky characterisation really appealed to me.
And I’m not talking about when she was 12 and I was 18, which is perhaps a little weird, but when I started to notice her from around the middle of the series’ run.
How’s this for obscure? The other day I stumbled into the IMDB entry for the Disney Channel’s Still the Beaver and flashed back to my 80s crush (age-appropriate!) on Kaleena Kiff, who played Wally Cleaver’s daughter.
Not very obscure around here, but I’m in lust with Kari Byron from Mythbusters…
I’d link, but there’s one NSFW image (finally!) on the google image page…
http ://images.google.com/images?q=kari+byron&hl=en&sourceid=mozilla-search&start=0
Joe
Susan Dey
Maureen McCormick
Jodie Foster
Penny, from Lost in Space. That would be Angela Cartwright Oh, so long ago. Don’t ask me why - I was very young and this was my favorite show.
In the last season of L.A. Law they introduced a new lawyer, a Greek-American named Melina Paros, played by Lisa Zane. Just for that reason I was heartbroken when the show was cancelled. HAWT!
In the first season or two of Babylon 5 there was this really hot bridge officer – or whatever you call that station command center where Sinclair/Sheridan gives orders like Kirk in his chair – at any rate, she was always there and looked incredibly yummy in her form-fitting ass-hugging uniform – I think she had red hair – she only had lines on rare occasions and I never recall hearing her addressed by name, so I don’t even know how to begin finding out what actress played her.
How obscure and geeky is that? 
Dr. Arcane (Mark Lindsay Chapman) from the old so-bad-it’s-good Swamp Thing series in the early 90s.
Not so obscure, but Methos (Peter Wingfield) from Highlander.
Sarek (Mark Lenard) from Star Trek: TOS
In the mid-90s, whe she was ~45 and I was ~23, I had a torrid affair with Thalia Assuras (in my mind), then an anchor of the late-night World News Now on CBS. Oh how I loved working nights, so I could catch glimpses of her delivering the news with the flair of someone who knows that almost no one is watching. I still fondly recall the time she and her co-anchor brought big recliners into the studio, popped popcorn, and reviewed movies based only on the trailer. They’d eat some popcorn and say things like, “Nah, I don’t think I’d like that one”. Oh, how I loved her!
Kim Richards from Hello Larry, Lydia Cornell from Too Close for Comfort, and especially Tricia Cast from It’s Your Move.
Clark Brandon was covering my walls as a teenager with Leif Garrett, Andry Gibb and Robbie Benson. He used to be on the Facts of Life and the Fitzpatricks and on the cover of Tiger Beat for a couple of years. Looking at him now… meh! how tastes change!
Not me, but a friend of mine (I swear!) tells me she had a crush on Optimus Prime when she was a kid.
Hell, who can blame her? I mean, it’s Optimus FUCKING Prime!
I had a crush on Vyvyan in The Young Ones. Ginger hair and metal studs in your forehead was strangely arousing to me as a teen.
Amanda Pays, the woman who played Theora Jones on the short-lived Max Headroom TV show. She ensured that there was far less than max headroom…in my boxers.
Matthew Waterhouse, who played Adric on the original “Doctor Who.”
Laurie Walters, Joannie of Eight is Enough.
I once heard a rumor – absolutely no substantiation – that he only got the part by being the director’s bum-boy.
Tygra from Thundercats (okay, who saw that coming?)
Bluegrass from Silverhawks
Sam Beckett & Al Calavicci from Quantum Leap
Riddler from Batman the Animated Series (not the latest one, the good one from the 90s)
…yeah, I go for geeky guys.
If animated characters count, my choice is Kim Possible!