Great thread
The titles are an integral part of the TV show and if you can get a catchy theme tune, even better. I like a lot of the ones already posted, including:
Whatever Happened To The Likely Lads, great theme song too.
Auf Wiedersehen Pet (Series 1 & 2), both had great theme songs, series one having one each for the opening and closing sequence.
Porridge (like this one as it tells the background to the premise of the programme, more later)
Randall & Hopkirk (Deceased), great title sequence with equally brilliant theme tune
The Fall & Rise Of Reginald Perrin
The Sweeney (Series 1-3, of course)
Minder (love the still of Arthur and Terry "holding" the lamp post up)
The Six Million Dollar Man (OK, a bit biased here but again, the title sequence gives you the premise of the show)
And just about every kids tv show/cartoon, such as Why Don't You, Grange Hill, Scooby Doo, The Pink Panther, Jamie & The Magic Torch, The Wombles, Aubrey to name but a few, but I love most of not all of them.