I was going to suggest White Russians, but that's basically a coffee-flavoured milkshake so not a good fit. So here's a few off the top of my head -- no shakers or blenders needed, just mix it up in a glass or a pitcher. I'm too lazy for that!
I'm quite fond of a
Blue Lagoon:
50 ml (1 2/3 fl oz) vodka
25 ml (7/8 fl oz) blue Curacao
100 ml (3 1/3 fl oz) lemonade
1 maraschino cherry
Optional: lime cordial
Ice
Actual amounts are very flexible, just stick with a similar ratio and you'll be fine. Finding blue Curaco (a sweet, bright blue syrup) is the hardest part, but if you have a supermarket with a cocktail section you should find it.
Also relatively easy is the
Mojito:
White Rum
Sugar Syrup (or white caster sugar)
Lime Juice (or fresh lime)
Soda Water (Sparkling Water)
Fresh Mint
Ratios are up to you -- I go heavy on soda water and sugar syrup, others go light on soda water and heavy on rum.
There are
lots of
recipes online.
A summer classic:
Pimms and Lemonade
Pour a decent amount of Pimms. Add LOTs of lemonade and lots of fruit (apples, cucumber, mint, orange, strawberries, whatever). Enjoy, and adjust ratios as you get steadily more drunk.
And here's a few I haven't tried much of at home, taken from the Wetherspoons menu because I'm a classy dame:
Bellini:
Prosecco (200ml) with a dash of peach snaps.
Gin Fiz:
Gin of your choice with elderflower cordial (adds sweetness), lime, tonic water.
Purple Rain
Sourz Cherry (no idea if Iceland has this, I'm sorry!)
Blue Curaco
Lemonade
Sex on the Beach:
Vodka
Peach Schnapps
Cranberry Juice
Orange Juice
Have a fantastic birthday, buddy!