For a topic like this, emphasising the need to do one's own research before investing in any shares cannot be over stated as especially these days and especially in the UK where investing in company shares is very risky.
My 6 own picks for 2019 are:
1. EVR Holdings (epic EVRH) - A UK company that could give rise to a British iTunes though its share price has been hit for weeks by shorting (the practice of selling shares which one does not own, in the hope of driving the share price down; then buying the shares back at a lower price and giving them back to the pension fund owners who probably did not know that their shares had been 'borrowed' in this way). Current (ie close of business on 14th December 2018) share price to buy is 6.25p (I hold a few)
2. Flybe (FLYB) The airline which after heavy losses has put itself up for sale. Possibly some bigger airline keen to secure Heathrow landing slots will put in a bid; though possibly not. Current sp is 18.5p.
3. Greatland Gold (GGP) An Australian gold miner which has decent looking survey results though no actual gold yet. Current sp is 1.70p.
4. CAP-XX Ltd - Designs and manufactures thin, flat supercapacitors and energy management systems used in portable and small-scale electronic devices. I believe another Australian based company. Currently 8.50p to buy.
5. Cluff Natural Resources plc (CLNR) A British North Sea oil hopeful. I have held shares in this co on and off (none at present) for months but so far simply "promises promises...". Still 2019 could be double or quits time. Currently 2.10p to buy.
6. Wey Education (WEY). This is or has been, one of my younger brother's favourite companies but its share price has been plummeting downwards upon the illness then untimely tragic death of its chairman. Currently 9p. to buy.
Do your own research!